diff --git a/examples/complete-vpc/main.tf b/examples/complete-vpc/main.tf
index cee1fbcc2..8e258912e 100644
--- a/examples/complete-vpc/main.tf
+++ b/examples/complete-vpc/main.tf
@@ -4,7 +4,7 @@ provider "aws" {
 
 data "aws_security_group" "default" {
   name   = "default"
-  vpc_id = "${module.vpc.vpc_id}"
+  vpc_id = module.vpc.vpc_id
 }
 
 module "vpc" {
@@ -45,37 +45,37 @@ module "vpc" {
   # VPC endpoint for SSM
   enable_ssm_endpoint              = true
   ssm_endpoint_private_dns_enabled = true
-  ssm_endpoint_security_group_ids  = ["${data.aws_security_group.default.id}"] # ssm_endpoint_subnet_ids = ["..."]
+  ssm_endpoint_security_group_ids  = [data.aws_security_group.default.id] # ssm_endpoint_subnet_ids = ["..."]
 
   # VPC endpoint for SSMMESSAGES
   enable_ssmmessages_endpoint              = true
   ssmmessages_endpoint_private_dns_enabled = true
-  ssmmessages_endpoint_security_group_ids  = ["${data.aws_security_group.default.id}"]
+  ssmmessages_endpoint_security_group_ids  = [data.aws_security_group.default.id]
 
   # VPC Endpoint for EC2
   enable_ec2_endpoint              = true
   ec2_endpoint_private_dns_enabled = true
-  ec2_endpoint_security_group_ids  = ["${data.aws_security_group.default.id}"]
+  ec2_endpoint_security_group_ids  = [data.aws_security_group.default.id]
 
   # VPC Endpoint for EC2MESSAGES
   enable_ec2messages_endpoint              = true
   ec2messages_endpoint_private_dns_enabled = true
-  ec2messages_endpoint_security_group_ids  = ["${data.aws_security_group.default.id}"]
+  ec2messages_endpoint_security_group_ids  = [data.aws_security_group.default.id]
 
   # VPC Endpoint for ECR API
   enable_ecr_api_endpoint              = true
   ecr_api_endpoint_private_dns_enabled = true
-  ecr_api_endpoint_security_group_ids  = ["${data.aws_security_group.default.id}"]
+  ecr_api_endpoint_security_group_ids  = [data.aws_security_group.default.id]
 
   # VPC Endpoint for ECR DKR
   enable_ecr_dkr_endpoint              = true
   ecr_dkr_endpoint_private_dns_enabled = true
-  ecr_dkr_endpoint_security_group_ids  = ["${data.aws_security_group.default.id}"]
+  ecr_dkr_endpoint_security_group_ids  = [data.aws_security_group.default.id]
 
   # VPC endpoint for KMS
   enable_kms_endpoint              = true
   kms_endpoint_private_dns_enabled = true
-  kms_endpoint_security_group_ids  = ["${data.aws_security_group.default.id}"]
+  kms_endpoint_security_group_ids  = [data.aws_security_group.default.id]
 
   # kms_endpoint_subnet_ids = ["..."]
 
@@ -85,3 +85,4 @@ module "vpc" {
     Name        = "complete"
   }
 }
+
diff --git a/examples/complete-vpc/outputs.tf b/examples/complete-vpc/outputs.tf
index 871359d39..db1fef127 100644
--- a/examples/complete-vpc/outputs.tf
+++ b/examples/complete-vpc/outputs.tf
@@ -1,60 +1,60 @@
 # VPC
 output "vpc_id" {
   description = "The ID of the VPC"
-  value       = "${module.vpc.vpc_id}"
+  value       = module.vpc.vpc_id
 }
 
 # Subnets
 output "private_subnets" {
   description = "List of IDs of private subnets"
-  value       = ["${module.vpc.private_subnets}"]
+  value       = module.vpc.private_subnets
 }
 
 output "public_subnets" {
   description = "List of IDs of public subnets"
-  value       = ["${module.vpc.public_subnets}"]
+  value       = module.vpc.public_subnets
 }
 
 output "database_subnets" {
   description = "List of IDs of database subnets"
-  value       = ["${module.vpc.database_subnets}"]
+  value       = module.vpc.database_subnets
 }
 
 output "elasticache_subnets" {
   description = "List of IDs of elasticache subnets"
-  value       = ["${module.vpc.elasticache_subnets}"]
+  value       = module.vpc.elasticache_subnets
 }
 
 output "redshift_subnets" {
   description = "List of IDs of redshift subnets"
-  value       = ["${module.vpc.redshift_subnets}"]
+  value       = module.vpc.redshift_subnets
 }
 
 output "intra_subnets" {
   description = "List of IDs of intra subnets"
-  value       = ["${module.vpc.intra_subnets}"]
+  value       = module.vpc.intra_subnets
 }
 
 # NAT gateways
 output "nat_public_ips" {
   description = "List of public Elastic IPs created for AWS NAT Gateway"
-  value       = ["${module.vpc.nat_public_ips}"]
+  value       = module.vpc.nat_public_ips
 }
 
 # VPC endpoints
 output "vpc_endpoint_ssm_id" {
   description = "The ID of VPC endpoint for SSM"
-  value       = "${module.vpc.vpc_endpoint_ssm_id}"
+  value       = module.vpc.vpc_endpoint_ssm_id
 }
 
 output "vpc_endpoint_ssm_network_interface_ids" {
   description = "One or more network interfaces for the VPC Endpoint for SSM."
-  value       = ["${module.vpc.vpc_endpoint_ssm_network_interface_ids}"]
+  value       = module.vpc.vpc_endpoint_ssm_network_interface_ids
 }
 
 output "vpc_endpoint_ssm_dns_entry" {
   description = "The DNS entries for the VPC Endpoint for SSM."
-  value       = ["${module.vpc.vpc_endpoint_ssm_dns_entry}"]
+  value       = module.vpc.vpc_endpoint_ssm_dns_entry
 }
 
 //
@@ -73,4 +73,3 @@ output "vpc_endpoint_ssm_dns_entry" {
 //  description = "The DNS entries for the VPC Endpoint for EC2."
 //  value = ["${module.vpc.vpc_endpoint_ec2_dns_entry}"]
 //}
-
diff --git a/examples/complete-vpc/versions.tf b/examples/complete-vpc/versions.tf
new file mode 100644
index 000000000..ac97c6ac8
--- /dev/null
+++ b/examples/complete-vpc/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}
diff --git a/examples/issue-108-route-already-exists/main.tf b/examples/issue-108-route-already-exists/main.tf
index 199b47a9f..74f0af0c6 100644
--- a/examples/issue-108-route-already-exists/main.tf
+++ b/examples/issue-108-route-already-exists/main.tf
@@ -19,3 +19,4 @@ module "vpc" {
   enable_s3_endpoint       = true
   enable_dynamodb_endpoint = true
 }
+
diff --git a/examples/issue-108-route-already-exists/outputs.tf b/examples/issue-108-route-already-exists/outputs.tf
index 26f69ebd4..51b4e83b7 100644
--- a/examples/issue-108-route-already-exists/outputs.tf
+++ b/examples/issue-108-route-already-exists/outputs.tf
@@ -1,32 +1,33 @@
 # VPC
 output "vpc_id" {
   description = "The ID of the VPC"
-  value       = "${module.vpc.vpc_id}"
+  value       = module.vpc.vpc_id
 }
 
 # Subnets
 output "private_subnets" {
   description = "List of IDs of private subnets"
-  value       = ["${module.vpc.private_subnets}"]
+  value       = module.vpc.private_subnets
 }
 
 output "public_subnets" {
   description = "List of IDs of public subnets"
-  value       = ["${module.vpc.public_subnets}"]
+  value       = module.vpc.public_subnets
 }
 
 output "database_subnets" {
   description = "List of IDs of database subnets"
-  value       = ["${module.vpc.database_subnets}"]
+  value       = module.vpc.database_subnets
 }
 
 output "elasticache_subnets" {
   description = "List of IDs of elasticache subnets"
-  value       = ["${module.vpc.elasticache_subnets}"]
+  value       = module.vpc.elasticache_subnets
 }
 
 # NAT gateways
 output "nat_public_ips" {
   description = "List of public Elastic IPs created for AWS NAT Gateway"
-  value       = ["${module.vpc.nat_public_ips}"]
+  value       = module.vpc.nat_public_ips
 }
+
diff --git a/examples/issue-108-route-already-exists/versions.tf b/examples/issue-108-route-already-exists/versions.tf
new file mode 100644
index 000000000..ac97c6ac8
--- /dev/null
+++ b/examples/issue-108-route-already-exists/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}
diff --git a/examples/issue-224-vpcendpoint-apigw/main.tf b/examples/issue-224-vpcendpoint-apigw/main.tf
index 252f885e7..2ae222af1 100644
--- a/examples/issue-224-vpcendpoint-apigw/main.tf
+++ b/examples/issue-224-vpcendpoint-apigw/main.tf
@@ -4,7 +4,7 @@ provider "aws" {
 
 data "aws_security_group" "default" {
   name   = "default"
-  vpc_id = "${module.vpc.vpc_id}"
+  vpc_id = module.vpc.vpc_id
 }
 
 module "vpc" {
@@ -19,7 +19,7 @@ module "vpc" {
 
   # VPC endpoint for API gateway
   enable_apigw_endpoint              = true
-  apigw_endpoint_security_group_ids  = ["${data.aws_security_group.default.id}"]
+  apigw_endpoint_security_group_ids  = [data.aws_security_group.default.id]
   apigw_endpoint_private_dns_enabled = true
 
   tags = {
@@ -28,3 +28,4 @@ module "vpc" {
     Name        = "test-224"
   }
 }
+
diff --git a/examples/issue-224-vpcendpoint-apigw/versions.tf b/examples/issue-224-vpcendpoint-apigw/versions.tf
new file mode 100644
index 000000000..ac97c6ac8
--- /dev/null
+++ b/examples/issue-224-vpcendpoint-apigw/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}
diff --git a/examples/issue-44-asymmetric-private-subnets/main.tf b/examples/issue-44-asymmetric-private-subnets/main.tf
index 1a1c4cf0c..07f3f0fe7 100644
--- a/examples/issue-44-asymmetric-private-subnets/main.tf
+++ b/examples/issue-44-asymmetric-private-subnets/main.tf
@@ -25,3 +25,4 @@ module "vpc" {
     Name  = "asymmetrical"
   }
 }
+
diff --git a/examples/issue-44-asymmetric-private-subnets/outputs.tf b/examples/issue-44-asymmetric-private-subnets/outputs.tf
index 26f69ebd4..51b4e83b7 100644
--- a/examples/issue-44-asymmetric-private-subnets/outputs.tf
+++ b/examples/issue-44-asymmetric-private-subnets/outputs.tf
@@ -1,32 +1,33 @@
 # VPC
 output "vpc_id" {
   description = "The ID of the VPC"
-  value       = "${module.vpc.vpc_id}"
+  value       = module.vpc.vpc_id
 }
 
 # Subnets
 output "private_subnets" {
   description = "List of IDs of private subnets"
-  value       = ["${module.vpc.private_subnets}"]
+  value       = module.vpc.private_subnets
 }
 
 output "public_subnets" {
   description = "List of IDs of public subnets"
-  value       = ["${module.vpc.public_subnets}"]
+  value       = module.vpc.public_subnets
 }
 
 output "database_subnets" {
   description = "List of IDs of database subnets"
-  value       = ["${module.vpc.database_subnets}"]
+  value       = module.vpc.database_subnets
 }
 
 output "elasticache_subnets" {
   description = "List of IDs of elasticache subnets"
-  value       = ["${module.vpc.elasticache_subnets}"]
+  value       = module.vpc.elasticache_subnets
 }
 
 # NAT gateways
 output "nat_public_ips" {
   description = "List of public Elastic IPs created for AWS NAT Gateway"
-  value       = ["${module.vpc.nat_public_ips}"]
+  value       = module.vpc.nat_public_ips
 }
+
diff --git a/examples/issue-44-asymmetric-private-subnets/versions.tf b/examples/issue-44-asymmetric-private-subnets/versions.tf
new file mode 100644
index 000000000..ac97c6ac8
--- /dev/null
+++ b/examples/issue-44-asymmetric-private-subnets/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}
diff --git a/examples/issue-46-no-private-subnets/main.tf b/examples/issue-46-no-private-subnets/main.tf
index 8cb816e4c..e9e5ec517 100644
--- a/examples/issue-46-no-private-subnets/main.tf
+++ b/examples/issue-46-no-private-subnets/main.tf
@@ -23,3 +23,4 @@ module "vpc" {
     Name  = "no-private-subnets"
   }
 }
+
diff --git a/examples/issue-46-no-private-subnets/outputs.tf b/examples/issue-46-no-private-subnets/outputs.tf
index 26f69ebd4..51b4e83b7 100644
--- a/examples/issue-46-no-private-subnets/outputs.tf
+++ b/examples/issue-46-no-private-subnets/outputs.tf
@@ -1,32 +1,33 @@
 # VPC
 output "vpc_id" {
   description = "The ID of the VPC"
-  value       = "${module.vpc.vpc_id}"
+  value       = module.vpc.vpc_id
 }
 
 # Subnets
 output "private_subnets" {
   description = "List of IDs of private subnets"
-  value       = ["${module.vpc.private_subnets}"]
+  value       = module.vpc.private_subnets
 }
 
 output "public_subnets" {
   description = "List of IDs of public subnets"
-  value       = ["${module.vpc.public_subnets}"]
+  value       = module.vpc.public_subnets
 }
 
 output "database_subnets" {
   description = "List of IDs of database subnets"
-  value       = ["${module.vpc.database_subnets}"]
+  value       = module.vpc.database_subnets
 }
 
 output "elasticache_subnets" {
   description = "List of IDs of elasticache subnets"
-  value       = ["${module.vpc.elasticache_subnets}"]
+  value       = module.vpc.elasticache_subnets
 }
 
 # NAT gateways
 output "nat_public_ips" {
   description = "List of public Elastic IPs created for AWS NAT Gateway"
-  value       = ["${module.vpc.nat_public_ips}"]
+  value       = module.vpc.nat_public_ips
 }
+
diff --git a/examples/issue-46-no-private-subnets/versions.tf b/examples/issue-46-no-private-subnets/versions.tf
new file mode 100644
index 000000000..ac97c6ac8
--- /dev/null
+++ b/examples/issue-46-no-private-subnets/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}
diff --git a/examples/manage-default-vpc/main.tf b/examples/manage-default-vpc/main.tf
index 73da2c763..5f645dd8e 100644
--- a/examples/manage-default-vpc/main.tf
+++ b/examples/manage-default-vpc/main.tf
@@ -11,3 +11,4 @@ module "vpc" {
   default_vpc_name                 = "default"
   default_vpc_enable_dns_hostnames = true
 }
+
diff --git a/examples/manage-default-vpc/outputs.tf b/examples/manage-default-vpc/outputs.tf
index f41e2d898..ce193dd8d 100644
--- a/examples/manage-default-vpc/outputs.tf
+++ b/examples/manage-default-vpc/outputs.tf
@@ -1,10 +1,11 @@
 # Default VPC
 output "default_vpc_id" {
   description = "The ID of the Default VPC"
-  value       = "${module.vpc.default_vpc_id}"
+  value       = module.vpc.default_vpc_id
 }
 
 output "default_vpc_cidr_block" {
   description = "The CIDR block of the VPC"
-  value       = "${module.vpc.default_vpc_cidr_block}"
+  value       = module.vpc.default_vpc_cidr_block
 }
+
diff --git a/examples/manage-default-vpc/versions.tf b/examples/manage-default-vpc/versions.tf
new file mode 100644
index 000000000..ac97c6ac8
--- /dev/null
+++ b/examples/manage-default-vpc/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}
diff --git a/examples/network-acls/main.tf b/examples/network-acls/main.tf
index 0e3f6a29c..c1a1dab90 100644
--- a/examples/network-acls/main.tf
+++ b/examples/network-acls/main.tf
@@ -15,8 +15,14 @@ module "vpc" {
   elasticache_subnets = ["10.0.201.0/24", "10.0.202.0/24", "10.0.203.0/24"]
 
   public_dedicated_network_acl = true
-  public_inbound_acl_rules     = "${concat(local.network_acls["default_inbound"], local.network_acls["public_inbound"])}"
-  public_outbound_acl_rules    = "${concat(local.network_acls["default_outbound"], local.network_acls["public_outbound"])}"
+  public_inbound_acl_rules = concat(
+    local.network_acls["default_inbound"],
+    local.network_acls["public_inbound"],
+  )
+  public_outbound_acl_rules = concat(
+    local.network_acls["default_outbound"],
+    local.network_acls["public_outbound"],
+  )
 
   private_dedicated_network_acl = true
 
@@ -51,7 +57,6 @@ locals {
         cidr_block  = "0.0.0.0/0"
       },
     ]
-
     default_outbound = [
       {
         rule_number = 900
@@ -62,7 +67,6 @@ locals {
         cidr_block  = "0.0.0.0/0"
       },
     ]
-
     public_inbound = [
       {
         rule_number = 100
@@ -97,7 +101,6 @@ locals {
         cidr_block  = "0.0.0.0/0"
       },
     ]
-
     public_outbound = [
       {
         rule_number = 100
@@ -134,3 +137,4 @@ locals {
     ]
   }
 }
+
diff --git a/examples/network-acls/outputs.tf b/examples/network-acls/outputs.tf
index 535d5f43e..577d73980 100644
--- a/examples/network-acls/outputs.tf
+++ b/examples/network-acls/outputs.tf
@@ -1,13 +1,13 @@
 # VPC
 output "vpc_id" {
   description = "The ID of the VPC"
-  value       = "${module.vpc.vpc_id}"
+  value       = module.vpc.vpc_id
 }
 
 # CIDR blocks
 output "vpc_cidr_block" {
   description = "The CIDR block of the VPC"
-  value       = ["${module.vpc.vpc_cidr_block}"]
+  value       = module.vpc.vpc_cidr_block
 }
 
 //output "vpc_ipv6_cidr_block" {
@@ -18,37 +18,38 @@ output "vpc_cidr_block" {
 # Subnets
 output "private_subnets" {
   description = "List of IDs of private subnets"
-  value       = ["${module.vpc.private_subnets}"]
+  value       = module.vpc.private_subnets
 }
 
 output "public_subnets" {
   description = "List of IDs of public subnets"
-  value       = ["${module.vpc.public_subnets}"]
+  value       = module.vpc.public_subnets
 }
 
 # NAT gateways
 output "nat_public_ips" {
   description = "List of public Elastic IPs created for AWS NAT Gateway"
-  value       = ["${module.vpc.nat_public_ips}"]
+  value       = module.vpc.nat_public_ips
 }
 
 # Network ACLs
 output "public_network_acl_id" {
   description = "ID of the public network ACL"
-  value       = "${module.vpc.public_network_acl_id}"
+  value       = module.vpc.public_network_acl_id
 }
 
 output "private_network_acl_id" {
   description = "ID of the private network ACL"
-  value       = "${module.vpc.private_network_acl_id}"
+  value       = module.vpc.private_network_acl_id
 }
 
 output "elasticache_network_acl_id" {
   description = "ID of the elasticache network ACL"
-  value       = "${module.vpc.elasticache_network_acl_id}"
+  value       = module.vpc.elasticache_network_acl_id
 }
 
 output "default_network_acl_id" {
   description = "The ID of the default network ACL"
-  value       = "${module.vpc.default_network_acl_id}"
+  value       = module.vpc.default_network_acl_id
 }
+
diff --git a/examples/network-acls/versions.tf b/examples/network-acls/versions.tf
new file mode 100644
index 000000000..ac97c6ac8
--- /dev/null
+++ b/examples/network-acls/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}
diff --git a/examples/secondary-cidr-blocks/main.tf b/examples/secondary-cidr-blocks/main.tf
index e4cc43231..a49b973de 100644
--- a/examples/secondary-cidr-blocks/main.tf
+++ b/examples/secondary-cidr-blocks/main.tf
@@ -31,3 +31,4 @@ module "vpc" {
     Name = "vpc-name"
   }
 }
+
diff --git a/examples/secondary-cidr-blocks/outputs.tf b/examples/secondary-cidr-blocks/outputs.tf
index 7cc6480d8..c110ed2ab 100644
--- a/examples/secondary-cidr-blocks/outputs.tf
+++ b/examples/secondary-cidr-blocks/outputs.tf
@@ -1,33 +1,34 @@
 # VPC
 output "vpc_id" {
   description = "The ID of the VPC"
-  value       = "${module.vpc.vpc_id}"
+  value       = module.vpc.vpc_id
 }
 
 # CIDR blocks
 output "vpc_cidr_block" {
   description = "The CIDR block of the VPC"
-  value       = ["${module.vpc.vpc_cidr_block}"]
+  value       = module.vpc.vpc_cidr_block
 }
 
 output "vpc_secondary_cidr_blocks" {
   description = "List of secondary CIDR blocks of the VPC"
-  value       = ["${module.vpc.vpc_secondary_cidr_blocks}"]
+  value       = module.vpc.vpc_secondary_cidr_blocks
 }
 
 # Subnets
 output "private_subnets" {
   description = "List of IDs of private subnets"
-  value       = ["${module.vpc.private_subnets}"]
+  value       = module.vpc.private_subnets
 }
 
 output "public_subnets" {
   description = "List of IDs of public subnets"
-  value       = ["${module.vpc.public_subnets}"]
+  value       = module.vpc.public_subnets
 }
 
 # NAT gateways
 output "nat_public_ips" {
   description = "List of public Elastic IPs created for AWS NAT Gateway"
-  value       = ["${module.vpc.nat_public_ips}"]
+  value       = module.vpc.nat_public_ips
 }
+
diff --git a/examples/secondary-cidr-blocks/versions.tf b/examples/secondary-cidr-blocks/versions.tf
new file mode 100644
index 000000000..ac97c6ac8
--- /dev/null
+++ b/examples/secondary-cidr-blocks/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}
diff --git a/examples/simple-vpc/main.tf b/examples/simple-vpc/main.tf
index decd0b0c5..c0b094835 100644
--- a/examples/simple-vpc/main.tf
+++ b/examples/simple-vpc/main.tf
@@ -4,7 +4,7 @@ provider "aws" {
 
 data "aws_security_group" "default" {
   name   = "default"
-  vpc_id = "${module.vpc.vpc_id}"
+  vpc_id = module.vpc.vpc_id
 }
 
 module "vpc" {
@@ -36,3 +36,4 @@ module "vpc" {
     Name = "vpc-name"
   }
 }
+
diff --git a/examples/simple-vpc/outputs.tf b/examples/simple-vpc/outputs.tf
index 7ab197f4a..251969ca2 100644
--- a/examples/simple-vpc/outputs.tf
+++ b/examples/simple-vpc/outputs.tf
@@ -1,13 +1,13 @@
 # VPC
 output "vpc_id" {
   description = "The ID of the VPC"
-  value       = "${module.vpc.vpc_id}"
+  value       = module.vpc.vpc_id
 }
 
 # CIDR blocks
 output "vpc_cidr_block" {
   description = "The CIDR block of the VPC"
-  value       = ["${module.vpc.vpc_cidr_block}"]
+  value       = module.vpc.vpc_cidr_block
 }
 
 //output "vpc_ipv6_cidr_block" {
@@ -18,22 +18,23 @@ output "vpc_cidr_block" {
 # Subnets
 output "private_subnets" {
   description = "List of IDs of private subnets"
-  value       = ["${module.vpc.private_subnets}"]
+  value       = module.vpc.private_subnets
 }
 
 output "public_subnets" {
   description = "List of IDs of public subnets"
-  value       = ["${module.vpc.public_subnets}"]
+  value       = module.vpc.public_subnets
 }
 
 # NAT gateways
 output "nat_public_ips" {
   description = "List of public Elastic IPs created for AWS NAT Gateway"
-  value       = ["${module.vpc.nat_public_ips}"]
+  value       = module.vpc.nat_public_ips
 }
 
 # AZs
 output "azs" {
   description = "A list of availability zones spefified as argument to this module"
-  value       = ["${module.vpc.azs}"]
+  value       = module.vpc.azs
 }
+
diff --git a/examples/simple-vpc/versions.tf b/examples/simple-vpc/versions.tf
new file mode 100644
index 000000000..ac97c6ac8
--- /dev/null
+++ b/examples/simple-vpc/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}
diff --git a/examples/test_fixture/main.tf b/examples/test_fixture/main.tf
index b0eb37ea0..5752aba2e 100644
--- a/examples/test_fixture/main.tf
+++ b/examples/test_fixture/main.tf
@@ -1,14 +1,15 @@
 provider "aws" {
-  region = "${var.region}"
+  region = var.region
 }
 
-data "aws_availability_zones" "available" {}
+data "aws_availability_zones" "available" {
+}
 
 module "vpc" {
   source             = "../.."
   name               = "test-example"
   cidr               = "10.0.0.0/16"
-  azs                = ["${data.aws_availability_zones.available.names[0]}", "${data.aws_availability_zones.available.names[1]}"]
+  azs                = [data.aws_availability_zones.available.names[0], data.aws_availability_zones.available.names[1]]
   private_subnets    = ["10.0.1.0/24", "10.0.2.0/24"]
   public_subnets     = ["10.0.101.0/24", "10.0.102.0/24"]
   enable_nat_gateway = true
@@ -19,3 +20,4 @@ module "vpc" {
     Environment = "dev"
   }
 }
+
diff --git a/examples/test_fixture/outputs.tf b/examples/test_fixture/outputs.tf
index 4c89ae958..c6ec3716b 100644
--- a/examples/test_fixture/outputs.tf
+++ b/examples/test_fixture/outputs.tf
@@ -1,4 +1,5 @@
 output "region" {
   description = "Region we created the resources in."
-  value       = "${var.region}"
+  value       = var.region
 }
+
diff --git a/examples/test_fixture/variables.tf b/examples/test_fixture/variables.tf
index a3986dc92..f8455295f 100644
--- a/examples/test_fixture/variables.tf
+++ b/examples/test_fixture/variables.tf
@@ -1,3 +1,4 @@
 variable "region" {
   default = "eu-west-1"
 }
+
diff --git a/examples/test_fixture/versions.tf b/examples/test_fixture/versions.tf
new file mode 100644
index 000000000..ac97c6ac8
--- /dev/null
+++ b/examples/test_fixture/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}
diff --git a/examples/vpc-separate-private-route-tables/main.tf b/examples/vpc-separate-private-route-tables/main.tf
index b380a4065..99d996840 100644
--- a/examples/vpc-separate-private-route-tables/main.tf
+++ b/examples/vpc-separate-private-route-tables/main.tf
@@ -29,3 +29,4 @@ module "vpc" {
     Name        = "separate-private-route-tables"
   }
 }
+
diff --git a/examples/vpc-separate-private-route-tables/outputs.tf b/examples/vpc-separate-private-route-tables/outputs.tf
index 1a4ba6073..fdd5e8d05 100644
--- a/examples/vpc-separate-private-route-tables/outputs.tf
+++ b/examples/vpc-separate-private-route-tables/outputs.tf
@@ -1,37 +1,38 @@
 # VPC
 output "vpc_id" {
   description = "The ID of the VPC"
-  value       = "${module.vpc.vpc_id}"
+  value       = module.vpc.vpc_id
 }
 
 # Subnets
 output "private_subnets" {
   description = "List of IDs of private subnets"
-  value       = ["${module.vpc.private_subnets}"]
+  value       = module.vpc.private_subnets
 }
 
 output "public_subnets" {
   description = "List of IDs of public subnets"
-  value       = ["${module.vpc.public_subnets}"]
+  value       = module.vpc.public_subnets
 }
 
 output "database_subnets" {
   description = "List of IDs of database subnets"
-  value       = ["${module.vpc.database_subnets}"]
+  value       = module.vpc.database_subnets
 }
 
 output "elasticache_subnets" {
   description = "List of IDs of elasticache subnets"
-  value       = ["${module.vpc.elasticache_subnets}"]
+  value       = module.vpc.elasticache_subnets
 }
 
 output "redshift_subnets" {
   description = "List of IDs of elasticache subnets"
-  value       = ["${module.vpc.redshift_subnets}"]
+  value       = module.vpc.redshift_subnets
 }
 
 # NAT gateways
 output "nat_public_ips" {
   description = "List of public Elastic IPs created for AWS NAT Gateway"
-  value       = ["${module.vpc.nat_public_ips}"]
+  value       = module.vpc.nat_public_ips
 }
+
diff --git a/examples/vpc-separate-private-route-tables/versions.tf b/examples/vpc-separate-private-route-tables/versions.tf
new file mode 100644
index 000000000..ac97c6ac8
--- /dev/null
+++ b/examples/vpc-separate-private-route-tables/versions.tf
@@ -0,0 +1,4 @@
+
+terraform {
+  required_version = ">= 0.12"
+}
diff --git a/main.tf b/main.tf
index 1b6f3fa42..9eb26d30c 100644
--- a/main.tf
+++ b/main.tf
@@ -1,91 +1,127 @@
 terraform {
-  required_version = ">= 0.10.3" # introduction of Local Values configuration language feature
+  required_version = ">= 0.12"
 }
 
 locals {
-  max_subnet_length = "${max(length(var.private_subnets), length(var.elasticache_subnets), length(var.database_subnets), length(var.redshift_subnets))}"
-  nat_gateway_count = "${var.single_nat_gateway ? 1 : (var.one_nat_gateway_per_az ? length(var.azs) : local.max_subnet_length)}"
+  max_subnet_length = max(
+    length(var.private_subnets),
+    length(var.elasticache_subnets),
+    length(var.database_subnets),
+    length(var.redshift_subnets),
+  )
+  nat_gateway_count = var.single_nat_gateway ? 1 : var.one_nat_gateway_per_az ? length(var.azs) : local.max_subnet_length
 
   # Use `local.vpc_id` to give a hint to Terraform that subnets should be deleted before secondary CIDR blocks can be free!
-  vpc_id = "${element(concat(aws_vpc_ipv4_cidr_block_association.this.*.vpc_id, aws_vpc.this.*.id, list("")), 0)}"
+  vpc_id = element(
+    concat(
+      aws_vpc_ipv4_cidr_block_association.this.*.vpc_id,
+      aws_vpc.this.*.id,
+      [""],
+    ),
+    0,
+  )
 }
 
 ######
 # VPC
 ######
 resource "aws_vpc" "this" {
-  count = "${var.create_vpc ? 1 : 0}"
+  count = var.create_vpc ? 1 : 0
 
-  cidr_block                       = "${var.cidr}"
-  instance_tenancy                 = "${var.instance_tenancy}"
-  enable_dns_hostnames             = "${var.enable_dns_hostnames}"
-  enable_dns_support               = "${var.enable_dns_support}"
-  assign_generated_ipv6_cidr_block = "${var.assign_generated_ipv6_cidr_block}"
+  cidr_block                       = var.cidr
+  instance_tenancy                 = var.instance_tenancy
+  enable_dns_hostnames             = var.enable_dns_hostnames
+  enable_dns_support               = var.enable_dns_support
+  assign_generated_ipv6_cidr_block = var.assign_generated_ipv6_cidr_block
 
-  tags = "${merge(map("Name", format("%s", var.name)), var.tags, var.vpc_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s", var.name)
+    },
+    var.tags,
+    var.vpc_tags,
+  )
 }
 
 resource "aws_vpc_ipv4_cidr_block_association" "this" {
-  count = "${var.create_vpc && length(var.secondary_cidr_blocks) > 0 ? length(var.secondary_cidr_blocks) : 0}"
+  count = var.create_vpc && length(var.secondary_cidr_blocks) > 0 ? length(var.secondary_cidr_blocks) : 0
 
-  vpc_id = "${aws_vpc.this.id}"
+  vpc_id = aws_vpc.this[0].id
 
-  cidr_block = "${element(var.secondary_cidr_blocks, count.index)}"
+  cidr_block = element(var.secondary_cidr_blocks, count.index)
 }
 
 ###################
 # DHCP Options Set
 ###################
 resource "aws_vpc_dhcp_options" "this" {
-  count = "${var.create_vpc && var.enable_dhcp_options ? 1 : 0}"
+  count = var.create_vpc && var.enable_dhcp_options ? 1 : 0
 
-  domain_name          = "${var.dhcp_options_domain_name}"
-  domain_name_servers  = ["${var.dhcp_options_domain_name_servers}"]
-  ntp_servers          = ["${var.dhcp_options_ntp_servers}"]
-  netbios_name_servers = ["${var.dhcp_options_netbios_name_servers}"]
-  netbios_node_type    = "${var.dhcp_options_netbios_node_type}"
+  domain_name          = var.dhcp_options_domain_name
+  domain_name_servers  = var.dhcp_options_domain_name_servers
+  ntp_servers          = var.dhcp_options_ntp_servers
+  netbios_name_servers = var.dhcp_options_netbios_name_servers
+  netbios_node_type    = var.dhcp_options_netbios_node_type
 
-  tags = "${merge(map("Name", format("%s", var.name)), var.tags, var.dhcp_options_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s", var.name)
+    },
+    var.tags,
+    var.dhcp_options_tags,
+  )
 }
 
 ###############################
 # DHCP Options Set Association
 ###############################
 resource "aws_vpc_dhcp_options_association" "this" {
-  count = "${var.create_vpc && var.enable_dhcp_options ? 1 : 0}"
+  count = var.create_vpc && var.enable_dhcp_options ? 1 : 0
 
-  vpc_id          = "${local.vpc_id}"
-  dhcp_options_id = "${aws_vpc_dhcp_options.this.id}"
+  vpc_id          = local.vpc_id
+  dhcp_options_id = aws_vpc_dhcp_options.this[0].id
 }
 
 ###################
 # Internet Gateway
 ###################
 resource "aws_internet_gateway" "this" {
-  count = "${var.create_vpc && length(var.public_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && length(var.public_subnets) > 0 ? 1 : 0
 
-  vpc_id = "${local.vpc_id}"
+  vpc_id = local.vpc_id
 
-  tags = "${merge(map("Name", format("%s", var.name)), var.tags, var.igw_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s", var.name)
+    },
+    var.tags,
+    var.igw_tags,
+  )
 }
 
 ################
 # Publiс routes
 ################
 resource "aws_route_table" "public" {
-  count = "${var.create_vpc && length(var.public_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && length(var.public_subnets) > 0 ? 1 : 0
 
-  vpc_id = "${local.vpc_id}"
+  vpc_id = local.vpc_id
 
-  tags = "${merge(map("Name", format("%s-${var.public_subnet_suffix}", var.name)), var.tags, var.public_route_table_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s-${var.public_subnet_suffix}", var.name)
+    },
+    var.tags,
+    var.public_route_table_tags,
+  )
 }
 
 resource "aws_route" "public_internet_gateway" {
-  count = "${var.create_vpc && length(var.public_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && length(var.public_subnets) > 0 ? 1 : 0
 
-  route_table_id         = "${aws_route_table.public.id}"
+  route_table_id         = aws_route_table.public[0].id
   destination_cidr_block = "0.0.0.0/0"
-  gateway_id             = "${aws_internet_gateway.this.id}"
+  gateway_id             = aws_internet_gateway.this[0].id
 
   timeouts {
     create = "5m"
@@ -97,16 +133,26 @@ resource "aws_route" "public_internet_gateway" {
 # There are as many routing tables as the number of NAT gateways
 #################
 resource "aws_route_table" "private" {
-  count = "${var.create_vpc && local.max_subnet_length > 0 ? local.nat_gateway_count : 0}"
-
-  vpc_id = "${local.vpc_id}"
-
-  tags = "${merge(map("Name", (var.single_nat_gateway ? "${var.name}-${var.private_subnet_suffix}" : format("%s-${var.private_subnet_suffix}-%s", var.name, element(var.azs, count.index)))), var.tags, var.private_route_table_tags)}"
+  count = var.create_vpc && local.max_subnet_length > 0 ? local.nat_gateway_count : 0
+
+  vpc_id = local.vpc_id
+
+  tags = merge(
+    {
+      "Name" = var.single_nat_gateway ? "${var.name}-${var.private_subnet_suffix}" : format(
+        "%s-${var.private_subnet_suffix}-%s",
+        var.name,
+        element(var.azs, count.index),
+      )
+    },
+    var.tags,
+    var.private_route_table_tags,
+  )
 
   lifecycle {
     # When attaching VPN gateways it is common to define aws_vpn_gateway_route_propagation
     # resources that manipulate the attributes of the routing table (typically for the private subnets)
-    ignore_changes = ["propagating_vgws"]
+    ignore_changes = [propagating_vgws]
   }
 }
 
@@ -114,19 +160,25 @@ resource "aws_route_table" "private" {
 # Database routes
 #################
 resource "aws_route_table" "database" {
-  count = "${var.create_vpc && var.create_database_subnet_route_table && length(var.database_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.create_database_subnet_route_table && length(var.database_subnets) > 0 ? 1 : 0
 
-  vpc_id = "${local.vpc_id}"
+  vpc_id = local.vpc_id
 
-  tags = "${merge(var.tags, var.database_route_table_tags, map("Name", "${var.name}-${var.database_subnet_suffix}"))}"
+  tags = merge(
+    var.tags,
+    var.database_route_table_tags,
+    {
+      "Name" = "${var.name}-${var.database_subnet_suffix}"
+    },
+  )
 }
 
 resource "aws_route" "database_internet_gateway" {
-  count = "${var.create_vpc && var.create_database_subnet_route_table && length(var.database_subnets) > 0 && var.create_database_internet_gateway_route && !var.create_database_nat_gateway_route ? 1 : 0}"
+  count = var.create_vpc && var.create_database_subnet_route_table && length(var.database_subnets) > 0 && var.create_database_internet_gateway_route && false == var.create_database_nat_gateway_route ? 1 : 0
 
-  route_table_id         = "${aws_route_table.database.id}"
+  route_table_id         = aws_route_table.database[0].id
   destination_cidr_block = "0.0.0.0/0"
-  gateway_id             = "${aws_internet_gateway.this.id}"
+  gateway_id             = aws_internet_gateway.this[0].id
 
   timeouts {
     create = "5m"
@@ -134,10 +186,10 @@ resource "aws_route" "database_internet_gateway" {
 }
 
 resource "aws_route" "database_nat_gateway" {
-  count                  = "${var.create_vpc && var.create_database_subnet_route_table && length(var.database_subnets) > 0 && !var.create_database_internet_gateway_route && var.create_database_nat_gateway_route && var.enable_nat_gateway ? local.nat_gateway_count : 0}"
-  route_table_id         = "${element(aws_route_table.private.*.id, count.index)}"
+  count                  = var.create_vpc && var.create_database_subnet_route_table && length(var.database_subnets) > 0 && false == var.create_database_internet_gateway_route && var.create_database_nat_gateway_route && var.enable_nat_gateway ? local.nat_gateway_count : 0
+  route_table_id         = element(aws_route_table.private.*.id, count.index)
   destination_cidr_block = "0.0.0.0/0"
-  nat_gateway_id         = "${element(aws_nat_gateway.this.*.id, count.index)}"
+  nat_gateway_id         = element(aws_nat_gateway.this.*.id, count.index)
 
   timeouts {
     create = "5m"
@@ -148,157 +200,279 @@ resource "aws_route" "database_nat_gateway" {
 # Redshift routes
 #################
 resource "aws_route_table" "redshift" {
-  count = "${var.create_vpc && var.create_redshift_subnet_route_table && length(var.redshift_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.create_redshift_subnet_route_table && length(var.redshift_subnets) > 0 ? 1 : 0
 
-  vpc_id = "${local.vpc_id}"
+  vpc_id = local.vpc_id
 
-  tags = "${merge(var.tags, var.redshift_route_table_tags, map("Name", "${var.name}-${var.redshift_subnet_suffix}"))}"
+  tags = merge(
+    var.tags,
+    var.redshift_route_table_tags,
+    {
+      "Name" = "${var.name}-${var.redshift_subnet_suffix}"
+    },
+  )
 }
 
 #################
 # Elasticache routes
 #################
 resource "aws_route_table" "elasticache" {
-  count = "${var.create_vpc && var.create_elasticache_subnet_route_table && length(var.elasticache_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.create_elasticache_subnet_route_table && length(var.elasticache_subnets) > 0 ? 1 : 0
 
-  vpc_id = "${local.vpc_id}"
+  vpc_id = local.vpc_id
 
-  tags = "${merge(var.tags, var.elasticache_route_table_tags, map("Name", "${var.name}-${var.elasticache_subnet_suffix}"))}"
+  tags = merge(
+    var.tags,
+    var.elasticache_route_table_tags,
+    {
+      "Name" = "${var.name}-${var.elasticache_subnet_suffix}"
+    },
+  )
 }
 
 #################
 # Intra routes
 #################
 resource "aws_route_table" "intra" {
-  count = "${var.create_vpc && length(var.intra_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && length(var.intra_subnets) > 0 ? 1 : 0
 
-  vpc_id = "${local.vpc_id}"
+  vpc_id = local.vpc_id
 
-  tags = "${merge(map("Name", "${var.name}-${var.intra_subnet_suffix}"), var.tags, var.intra_route_table_tags)}"
+  tags = merge(
+    {
+      "Name" = "${var.name}-${var.intra_subnet_suffix}"
+    },
+    var.tags,
+    var.intra_route_table_tags,
+  )
 }
 
 ################
 # Public subnet
 ################
 resource "aws_subnet" "public" {
-  count = "${var.create_vpc && length(var.public_subnets) > 0 && (!var.one_nat_gateway_per_az || length(var.public_subnets) >= length(var.azs)) ? length(var.public_subnets) : 0}"
-
-  vpc_id                  = "${local.vpc_id}"
-  cidr_block              = "${element(concat(var.public_subnets, list("")), count.index)}"
-  availability_zone       = "${element(var.azs, count.index)}"
-  map_public_ip_on_launch = "${var.map_public_ip_on_launch}"
-
-  tags = "${merge(map("Name", format("%s-${var.public_subnet_suffix}-%s", var.name, element(var.azs, count.index))), var.tags, var.public_subnet_tags)}"
+  count = var.create_vpc && length(var.public_subnets) > 0 && false == var.one_nat_gateway_per_az || length(var.public_subnets) >= length(var.azs) ? length(var.public_subnets) : 0
+
+  vpc_id                  = local.vpc_id
+  cidr_block              = element(concat(var.public_subnets, [""]), count.index)
+  availability_zone       = element(var.azs, count.index)
+  map_public_ip_on_launch = var.map_public_ip_on_launch
+
+  tags = merge(
+    {
+      "Name" = format(
+        "%s-${var.public_subnet_suffix}-%s",
+        var.name,
+        element(var.azs, count.index),
+      )
+    },
+    var.tags,
+    var.public_subnet_tags,
+  )
 }
 
 #################
 # Private subnet
 #################
 resource "aws_subnet" "private" {
-  count = "${var.create_vpc && length(var.private_subnets) > 0 ? length(var.private_subnets) : 0}"
+  count = var.create_vpc && length(var.private_subnets) > 0 ? length(var.private_subnets) : 0
 
-  vpc_id            = "${local.vpc_id}"
-  cidr_block        = "${var.private_subnets[count.index]}"
-  availability_zone = "${element(var.azs, count.index)}"
+  vpc_id            = local.vpc_id
+  cidr_block        = var.private_subnets[count.index]
+  availability_zone = element(var.azs, count.index)
 
-  tags = "${merge(map("Name", format("%s-${var.private_subnet_suffix}-%s", var.name, element(var.azs, count.index))), var.tags, var.private_subnet_tags)}"
+  tags = merge(
+    {
+      "Name" = format(
+        "%s-${var.private_subnet_suffix}-%s",
+        var.name,
+        element(var.azs, count.index),
+      )
+    },
+    var.tags,
+    var.private_subnet_tags,
+  )
 }
 
 ##################
 # Database subnet
 ##################
 resource "aws_subnet" "database" {
-  count = "${var.create_vpc && length(var.database_subnets) > 0 ? length(var.database_subnets) : 0}"
+  count = var.create_vpc && length(var.database_subnets) > 0 ? length(var.database_subnets) : 0
 
-  vpc_id            = "${local.vpc_id}"
-  cidr_block        = "${var.database_subnets[count.index]}"
-  availability_zone = "${element(var.azs, count.index)}"
+  vpc_id            = local.vpc_id
+  cidr_block        = var.database_subnets[count.index]
+  availability_zone = element(var.azs, count.index)
 
-  tags = "${merge(map("Name", format("%s-${var.database_subnet_suffix}-%s", var.name, element(var.azs, count.index))), var.tags, var.database_subnet_tags)}"
+  tags = merge(
+    {
+      "Name" = format(
+        "%s-${var.database_subnet_suffix}-%s",
+        var.name,
+        element(var.azs, count.index),
+      )
+    },
+    var.tags,
+    var.database_subnet_tags,
+  )
 }
 
 resource "aws_db_subnet_group" "database" {
-  count = "${var.create_vpc && length(var.database_subnets) > 0 && var.create_database_subnet_group ? 1 : 0}"
+  count = var.create_vpc && length(var.database_subnets) > 0 && var.create_database_subnet_group ? 1 : 0
 
-  name        = "${lower(var.name)}"
+  name        = lower(var.name)
   description = "Database subnet group for ${var.name}"
-  subnet_ids  = ["${aws_subnet.database.*.id}"]
+  subnet_ids  = aws_subnet.database.*.id
 
-  tags = "${merge(map("Name", format("%s", var.name)), var.tags, var.database_subnet_group_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s", var.name)
+    },
+    var.tags,
+    var.database_subnet_group_tags,
+  )
 }
 
 ##################
 # Redshift subnet
 ##################
 resource "aws_subnet" "redshift" {
-  count = "${var.create_vpc && length(var.redshift_subnets) > 0 ? length(var.redshift_subnets) : 0}"
+  count = var.create_vpc && length(var.redshift_subnets) > 0 ? length(var.redshift_subnets) : 0
 
-  vpc_id            = "${local.vpc_id}"
-  cidr_block        = "${var.redshift_subnets[count.index]}"
-  availability_zone = "${element(var.azs, count.index)}"
+  vpc_id            = local.vpc_id
+  cidr_block        = var.redshift_subnets[count.index]
+  availability_zone = element(var.azs, count.index)
 
-  tags = "${merge(map("Name", format("%s-${var.redshift_subnet_suffix}-%s", var.name, element(var.azs, count.index))), var.tags, var.redshift_subnet_tags)}"
+  tags = merge(
+    {
+      "Name" = format(
+        "%s-${var.redshift_subnet_suffix}-%s",
+        var.name,
+        element(var.azs, count.index),
+      )
+    },
+    var.tags,
+    var.redshift_subnet_tags,
+  )
 }
 
 resource "aws_redshift_subnet_group" "redshift" {
-  count = "${var.create_vpc && length(var.redshift_subnets) > 0 && var.create_redshift_subnet_group ? 1 : 0}"
+  count = var.create_vpc && length(var.redshift_subnets) > 0 && var.create_redshift_subnet_group ? 1 : 0
 
-  name        = "${lower(var.name)}"
+  name        = lower(var.name)
   description = "Redshift subnet group for ${var.name}"
-  subnet_ids  = ["${aws_subnet.redshift.*.id}"]
+  subnet_ids  = aws_subnet.redshift.*.id
 
-  tags = "${merge(map("Name", format("%s", var.name)), var.tags, var.redshift_subnet_group_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s", var.name)
+    },
+    var.tags,
+    var.redshift_subnet_group_tags,
+  )
 }
 
 #####################
 # ElastiCache subnet
 #####################
 resource "aws_subnet" "elasticache" {
-  count = "${var.create_vpc && length(var.elasticache_subnets) > 0 ? length(var.elasticache_subnets) : 0}"
+  count = var.create_vpc && length(var.elasticache_subnets) > 0 ? length(var.elasticache_subnets) : 0
 
-  vpc_id            = "${local.vpc_id}"
-  cidr_block        = "${var.elasticache_subnets[count.index]}"
-  availability_zone = "${element(var.azs, count.index)}"
+  vpc_id            = local.vpc_id
+  cidr_block        = var.elasticache_subnets[count.index]
+  availability_zone = element(var.azs, count.index)
 
-  tags = "${merge(map("Name", format("%s-${var.elasticache_subnet_suffix}-%s", var.name, element(var.azs, count.index))), var.tags, var.elasticache_subnet_tags)}"
+  tags = merge(
+    {
+      "Name" = format(
+        "%s-${var.elasticache_subnet_suffix}-%s",
+        var.name,
+        element(var.azs, count.index),
+      )
+    },
+    var.tags,
+    var.elasticache_subnet_tags,
+  )
 }
 
 resource "aws_elasticache_subnet_group" "elasticache" {
-  count = "${var.create_vpc && length(var.elasticache_subnets) > 0 && var.create_elasticache_subnet_group ? 1 : 0}"
+  count = var.create_vpc && length(var.elasticache_subnets) > 0 && var.create_elasticache_subnet_group ? 1 : 0
 
-  name        = "${var.name}"
+  name        = var.name
   description = "ElastiCache subnet group for ${var.name}"
-  subnet_ids  = ["${aws_subnet.elasticache.*.id}"]
+  subnet_ids  = aws_subnet.elasticache.*.id
 }
 
 #####################################################
 # intra subnets - private subnet without NAT gateway
 #####################################################
 resource "aws_subnet" "intra" {
-  count = "${var.create_vpc && length(var.intra_subnets) > 0 ? length(var.intra_subnets) : 0}"
+  count = var.create_vpc && length(var.intra_subnets) > 0 ? length(var.intra_subnets) : 0
 
-  vpc_id            = "${local.vpc_id}"
-  cidr_block        = "${var.intra_subnets[count.index]}"
-  availability_zone = "${element(var.azs, count.index)}"
+  vpc_id            = local.vpc_id
+  cidr_block        = var.intra_subnets[count.index]
+  availability_zone = element(var.azs, count.index)
 
-  tags = "${merge(map("Name", format("%s-${var.intra_subnet_suffix}-%s", var.name, element(var.azs, count.index))), var.tags, var.intra_subnet_tags)}"
+  tags = merge(
+    {
+      "Name" = format(
+        "%s-${var.intra_subnet_suffix}-%s",
+        var.name,
+        element(var.azs, count.index),
+      )
+    },
+    var.tags,
+    var.intra_subnet_tags,
+  )
 }
 
 #######################
 # Default Network ACLs
 #######################
 resource "aws_default_network_acl" "this" {
-  count = "${var.create_vpc && var.manage_default_network_acl ? 1 : 0}"
-
-  default_network_acl_id = "${element(concat(aws_vpc.this.*.default_network_acl_id, list("")), 0)}"
-
-  ingress = "${var.default_network_acl_ingress}"
-  egress  = "${var.default_network_acl_egress}"
+  count = var.create_vpc && var.manage_default_network_acl ? 1 : 0
+
+  default_network_acl_id = element(concat(aws_vpc.this.*.default_network_acl_id, [""]), 0)
+
+  dynamic "ingress" {
+    for_each = var.default_network_acl_ingress
+    content {
+      action          = ingress.value.action
+      cidr_block      = lookup(ingress.value, "cidr_block", null)
+      from_port       = ingress.value.from_port
+      icmp_code       = lookup(ingress.value, "icmp_code", null)
+      icmp_type       = lookup(ingress.value, "icmp_type", null)
+      ipv6_cidr_block = lookup(ingress.value, "ipv6_cidr_block", null)
+      protocol        = ingress.value.protocol
+      rule_no         = ingress.value.rule_no
+      to_port         = ingress.value.to_port
+    }
+  }
+  dynamic "egress" {
+    for_each = var.default_network_acl_egress
+    content {
+      action          = egress.value.action
+      cidr_block      = lookup(egress.value, "cidr_block", null)
+      from_port       = egress.value.from_port
+      icmp_code       = lookup(egress.value, "icmp_code", null)
+      icmp_type       = lookup(egress.value, "icmp_type", null)
+      ipv6_cidr_block = lookup(egress.value, "ipv6_cidr_block", null)
+      protocol        = egress.value.protocol
+      rule_no         = egress.value.rule_no
+      to_port         = egress.value.to_port
+    }
+  }
 
-  tags = "${merge(map("Name", format("%s", var.default_network_acl_name)), var.tags, var.default_network_acl_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s", var.default_network_acl_name)
+    },
+    var.tags,
+    var.default_network_acl_tags,
+  )
 
   lifecycle {
-    ignore_changes = ["subnet_ids"]
+    ignore_changes = [subnet_ids]
   }
 }
 
@@ -306,240 +480,276 @@ resource "aws_default_network_acl" "this" {
 # Public Network ACLs
 ########################
 resource "aws_network_acl" "public" {
-  count = "${var.create_vpc && var.public_dedicated_network_acl && length(var.public_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.public_dedicated_network_acl && length(var.public_subnets) > 0 ? 1 : 0
 
-  vpc_id     = "${element(concat(aws_vpc.this.*.id, list("")), 0)}"
-  subnet_ids = ["${aws_subnet.public.*.id}"]
+  vpc_id     = element(concat(aws_vpc.this.*.id, [""]), 0)
+  subnet_ids = aws_subnet.public.*.id
 
-  tags = "${merge(map("Name", format("%s-${var.public_subnet_suffix}", var.name)), var.tags, var.public_acl_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s-${var.public_subnet_suffix}", var.name)
+    },
+    var.tags,
+    var.public_acl_tags,
+  )
 }
 
 resource "aws_network_acl_rule" "public_inbound" {
-  count = "${var.create_vpc && var.public_dedicated_network_acl && length(var.public_subnets) > 0 ? length(var.public_inbound_acl_rules) : 0}"
+  count = var.create_vpc && var.public_dedicated_network_acl && length(var.public_subnets) > 0 ? length(var.public_inbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.public.id}"
+  network_acl_id = aws_network_acl.public[0].id
 
   egress      = false
-  rule_number = "${lookup(var.public_inbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.public_inbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.public_inbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.public_inbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.public_inbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.public_inbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.public_inbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.public_inbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.public_inbound_acl_rules[count.index]["from_port"]
+  to_port     = var.public_inbound_acl_rules[count.index]["to_port"]
+  protocol    = var.public_inbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.public_inbound_acl_rules[count.index]["cidr_block"]
 }
 
 resource "aws_network_acl_rule" "public_outbound" {
-  count = "${var.create_vpc && var.public_dedicated_network_acl && length(var.public_subnets) > 0 ? length(var.public_outbound_acl_rules) : 0}"
+  count = var.create_vpc && var.public_dedicated_network_acl && length(var.public_subnets) > 0 ? length(var.public_outbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.public.id}"
+  network_acl_id = aws_network_acl.public[0].id
 
   egress      = true
-  rule_number = "${lookup(var.public_outbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.public_outbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.public_outbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.public_outbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.public_outbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.public_outbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.public_outbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.public_outbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.public_outbound_acl_rules[count.index]["from_port"]
+  to_port     = var.public_outbound_acl_rules[count.index]["to_port"]
+  protocol    = var.public_outbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.public_outbound_acl_rules[count.index]["cidr_block"]
 }
 
 #######################
 # Private Network ACLs
 #######################
 resource "aws_network_acl" "private" {
-  count = "${var.create_vpc && var.private_dedicated_network_acl && length(var.private_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.private_dedicated_network_acl && length(var.private_subnets) > 0 ? 1 : 0
 
-  vpc_id     = "${element(concat(aws_vpc.this.*.id, list("")), 0)}"
-  subnet_ids = ["${aws_subnet.private.*.id}"]
+  vpc_id     = element(concat(aws_vpc.this.*.id, [""]), 0)
+  subnet_ids = aws_subnet.private.*.id
 
-  tags = "${merge(map("Name", format("%s-${var.private_subnet_suffix}", var.name)), var.tags, var.private_acl_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s-${var.private_subnet_suffix}", var.name)
+    },
+    var.tags,
+    var.private_acl_tags,
+  )
 }
 
 resource "aws_network_acl_rule" "private_inbound" {
-  count = "${var.create_vpc && var.private_dedicated_network_acl && length(var.private_subnets) > 0 ? length(var.private_inbound_acl_rules) : 0}"
+  count = var.create_vpc && var.private_dedicated_network_acl && length(var.private_subnets) > 0 ? length(var.private_inbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.private.id}"
+  network_acl_id = aws_network_acl.private[0].id
 
   egress      = false
-  rule_number = "${lookup(var.private_inbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.private_inbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.private_inbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.private_inbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.private_inbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.private_inbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.private_inbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.private_inbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.private_inbound_acl_rules[count.index]["from_port"]
+  to_port     = var.private_inbound_acl_rules[count.index]["to_port"]
+  protocol    = var.private_inbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.private_inbound_acl_rules[count.index]["cidr_block"]
 }
 
 resource "aws_network_acl_rule" "private_outbound" {
-  count = "${var.create_vpc && var.private_dedicated_network_acl && length(var.private_subnets) > 0 ? length(var.private_outbound_acl_rules) : 0}"
+  count = var.create_vpc && var.private_dedicated_network_acl && length(var.private_subnets) > 0 ? length(var.private_outbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.private.id}"
+  network_acl_id = aws_network_acl.private[0].id
 
   egress      = true
-  rule_number = "${lookup(var.private_outbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.private_outbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.private_outbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.private_outbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.private_outbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.private_outbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.private_outbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.private_outbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.private_outbound_acl_rules[count.index]["from_port"]
+  to_port     = var.private_outbound_acl_rules[count.index]["to_port"]
+  protocol    = var.private_outbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.private_outbound_acl_rules[count.index]["cidr_block"]
 }
 
 ########################
 # Intra Network ACLs
 ########################
 resource "aws_network_acl" "intra" {
-  count = "${var.create_vpc && var.intra_dedicated_network_acl && length(var.intra_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.intra_dedicated_network_acl && length(var.intra_subnets) > 0 ? 1 : 0
 
-  vpc_id     = "${element(concat(aws_vpc.this.*.id, list("")), 0)}"
-  subnet_ids = ["${aws_subnet.intra.*.id}"]
+  vpc_id     = element(concat(aws_vpc.this.*.id, [""]), 0)
+  subnet_ids = aws_subnet.intra.*.id
 
-  tags = "${merge(map("Name", format("%s-${var.intra_subnet_suffix}", var.name)), var.tags, var.intra_acl_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s-${var.intra_subnet_suffix}", var.name)
+    },
+    var.tags,
+    var.intra_acl_tags,
+  )
 }
 
 resource "aws_network_acl_rule" "intra_inbound" {
-  count = "${var.create_vpc && var.intra_dedicated_network_acl && length(var.intra_subnets) > 0 ? length(var.intra_inbound_acl_rules) : 0}"
+  count = var.create_vpc && var.intra_dedicated_network_acl && length(var.intra_subnets) > 0 ? length(var.intra_inbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.intra.id}"
+  network_acl_id = aws_network_acl.intra[0].id
 
   egress      = false
-  rule_number = "${lookup(var.intra_inbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.intra_inbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.intra_inbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.intra_inbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.intra_inbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.intra_inbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.intra_inbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.intra_inbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.intra_inbound_acl_rules[count.index]["from_port"]
+  to_port     = var.intra_inbound_acl_rules[count.index]["to_port"]
+  protocol    = var.intra_inbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.intra_inbound_acl_rules[count.index]["cidr_block"]
 }
 
 resource "aws_network_acl_rule" "intra_outbound" {
-  count = "${var.create_vpc && var.intra_dedicated_network_acl && length(var.intra_subnets) > 0 ? length(var.intra_outbound_acl_rules) : 0}"
+  count = var.create_vpc && var.intra_dedicated_network_acl && length(var.intra_subnets) > 0 ? length(var.intra_outbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.intra.id}"
+  network_acl_id = aws_network_acl.intra[0].id
 
   egress      = true
-  rule_number = "${lookup(var.intra_outbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.intra_outbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.intra_outbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.intra_outbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.intra_outbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.intra_outbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.intra_outbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.intra_outbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.intra_outbound_acl_rules[count.index]["from_port"]
+  to_port     = var.intra_outbound_acl_rules[count.index]["to_port"]
+  protocol    = var.intra_outbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.intra_outbound_acl_rules[count.index]["cidr_block"]
 }
 
 ########################
 # Database Network ACLs
 ########################
 resource "aws_network_acl" "database" {
-  count = "${var.create_vpc && var.database_dedicated_network_acl && length(var.database_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.database_dedicated_network_acl && length(var.database_subnets) > 0 ? 1 : 0
 
-  vpc_id     = "${element(concat(aws_vpc.this.*.id, list("")), 0)}"
-  subnet_ids = ["${aws_subnet.database.*.id}"]
+  vpc_id     = element(concat(aws_vpc.this.*.id, [""]), 0)
+  subnet_ids = aws_subnet.database.*.id
 
-  tags = "${merge(map("Name", format("%s-${var.database_subnet_suffix}", var.name)), var.tags, var.database_acl_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s-${var.database_subnet_suffix}", var.name)
+    },
+    var.tags,
+    var.database_acl_tags,
+  )
 }
 
 resource "aws_network_acl_rule" "database_inbound" {
-  count = "${var.create_vpc && var.database_dedicated_network_acl && length(var.database_subnets) > 0 ? length(var.database_inbound_acl_rules) : 0}"
+  count = var.create_vpc && var.database_dedicated_network_acl && length(var.database_subnets) > 0 ? length(var.database_inbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.database.id}"
+  network_acl_id = aws_network_acl.database[0].id
 
   egress      = false
-  rule_number = "${lookup(var.database_inbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.database_inbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.database_inbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.database_inbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.database_inbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.database_inbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.database_inbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.database_inbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.database_inbound_acl_rules[count.index]["from_port"]
+  to_port     = var.database_inbound_acl_rules[count.index]["to_port"]
+  protocol    = var.database_inbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.database_inbound_acl_rules[count.index]["cidr_block"]
 }
 
 resource "aws_network_acl_rule" "database_outbound" {
-  count = "${var.create_vpc && var.database_dedicated_network_acl && length(var.database_subnets) > 0 ? length(var.database_outbound_acl_rules) : 0}"
+  count = var.create_vpc && var.database_dedicated_network_acl && length(var.database_subnets) > 0 ? length(var.database_outbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.database.id}"
+  network_acl_id = aws_network_acl.database[0].id
 
   egress      = true
-  rule_number = "${lookup(var.database_outbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.database_outbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.database_outbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.database_outbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.database_outbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.database_outbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.database_outbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.database_outbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.database_outbound_acl_rules[count.index]["from_port"]
+  to_port     = var.database_outbound_acl_rules[count.index]["to_port"]
+  protocol    = var.database_outbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.database_outbound_acl_rules[count.index]["cidr_block"]
 }
 
 ########################
 # Redshift Network ACLs
 ########################
 resource "aws_network_acl" "redshift" {
-  count = "${var.create_vpc && var.redshift_dedicated_network_acl && length(var.redshift_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.redshift_dedicated_network_acl && length(var.redshift_subnets) > 0 ? 1 : 0
 
-  vpc_id     = "${element(concat(aws_vpc.this.*.id, list("")), 0)}"
-  subnet_ids = ["${aws_subnet.redshift.*.id}"]
+  vpc_id     = element(concat(aws_vpc.this.*.id, [""]), 0)
+  subnet_ids = aws_subnet.redshift.*.id
 
-  tags = "${merge(map("Name", format("%s-${var.redshift_subnet_suffix}", var.name)), var.tags, var.redshift_acl_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s-${var.redshift_subnet_suffix}", var.name)
+    },
+    var.tags,
+    var.redshift_acl_tags,
+  )
 }
 
 resource "aws_network_acl_rule" "redshift_inbound" {
-  count = "${var.create_vpc && var.redshift_dedicated_network_acl && length(var.redshift_subnets) > 0 ? length(var.redshift_inbound_acl_rules) : 0}"
+  count = var.create_vpc && var.redshift_dedicated_network_acl && length(var.redshift_subnets) > 0 ? length(var.redshift_inbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.redshift.id}"
+  network_acl_id = aws_network_acl.redshift[0].id
 
   egress      = false
-  rule_number = "${lookup(var.redshift_inbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.redshift_inbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.redshift_inbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.redshift_inbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.redshift_inbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.redshift_inbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.redshift_inbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.redshift_inbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.redshift_inbound_acl_rules[count.index]["from_port"]
+  to_port     = var.redshift_inbound_acl_rules[count.index]["to_port"]
+  protocol    = var.redshift_inbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.redshift_inbound_acl_rules[count.index]["cidr_block"]
 }
 
 resource "aws_network_acl_rule" "redshift_outbound" {
-  count = "${var.create_vpc && var.redshift_dedicated_network_acl && length(var.redshift_subnets) > 0 ? length(var.redshift_outbound_acl_rules) : 0}"
+  count = var.create_vpc && var.redshift_dedicated_network_acl && length(var.redshift_subnets) > 0 ? length(var.redshift_outbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.redshift.id}"
+  network_acl_id = aws_network_acl.redshift[0].id
 
   egress      = true
-  rule_number = "${lookup(var.redshift_outbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.redshift_outbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.redshift_outbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.redshift_outbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.redshift_outbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.redshift_outbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.redshift_outbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.redshift_outbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.redshift_outbound_acl_rules[count.index]["from_port"]
+  to_port     = var.redshift_outbound_acl_rules[count.index]["to_port"]
+  protocol    = var.redshift_outbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.redshift_outbound_acl_rules[count.index]["cidr_block"]
 }
 
 ###########################
 # Elasticache Network ACLs
 ###########################
 resource "aws_network_acl" "elasticache" {
-  count = "${var.create_vpc && var.elasticache_dedicated_network_acl && length(var.elasticache_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.elasticache_dedicated_network_acl && length(var.elasticache_subnets) > 0 ? 1 : 0
 
-  vpc_id     = "${element(concat(aws_vpc.this.*.id, list("")), 0)}"
-  subnet_ids = ["${aws_subnet.elasticache.*.id}"]
+  vpc_id     = element(concat(aws_vpc.this.*.id, [""]), 0)
+  subnet_ids = aws_subnet.elasticache.*.id
 
-  tags = "${merge(map("Name", format("%s-${var.elasticache_subnet_suffix}", var.name)), var.tags, var.elasticache_acl_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s-${var.elasticache_subnet_suffix}", var.name)
+    },
+    var.tags,
+    var.elasticache_acl_tags,
+  )
 }
 
 resource "aws_network_acl_rule" "elasticache_inbound" {
-  count = "${var.create_vpc && var.elasticache_dedicated_network_acl && length(var.elasticache_subnets) > 0 ? length(var.elasticache_inbound_acl_rules) : 0}"
+  count = var.create_vpc && var.elasticache_dedicated_network_acl && length(var.elasticache_subnets) > 0 ? length(var.elasticache_inbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.elasticache.id}"
+  network_acl_id = aws_network_acl.elasticache[0].id
 
   egress      = false
-  rule_number = "${lookup(var.elasticache_inbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.elasticache_inbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.elasticache_inbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.elasticache_inbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.elasticache_inbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.elasticache_inbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.elasticache_inbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.elasticache_inbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.elasticache_inbound_acl_rules[count.index]["from_port"]
+  to_port     = var.elasticache_inbound_acl_rules[count.index]["to_port"]
+  protocol    = var.elasticache_inbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.elasticache_inbound_acl_rules[count.index]["cidr_block"]
 }
 
 resource "aws_network_acl_rule" "elasticache_outbound" {
-  count = "${var.create_vpc && var.elasticache_dedicated_network_acl && length(var.elasticache_subnets) > 0 ? length(var.elasticache_outbound_acl_rules) : 0}"
+  count = var.create_vpc && var.elasticache_dedicated_network_acl && length(var.elasticache_subnets) > 0 ? length(var.elasticache_outbound_acl_rules) : 0
 
-  network_acl_id = "${aws_network_acl.elasticache.id}"
+  network_acl_id = aws_network_acl.elasticache[0].id
 
   egress      = true
-  rule_number = "${lookup(var.elasticache_outbound_acl_rules[count.index], "rule_number")}"
-  rule_action = "${lookup(var.elasticache_outbound_acl_rules[count.index], "rule_action")}"
-  from_port   = "${lookup(var.elasticache_outbound_acl_rules[count.index], "from_port")}"
-  to_port     = "${lookup(var.elasticache_outbound_acl_rules[count.index], "to_port")}"
-  protocol    = "${lookup(var.elasticache_outbound_acl_rules[count.index], "protocol")}"
-  cidr_block  = "${lookup(var.elasticache_outbound_acl_rules[count.index], "cidr_block")}"
+  rule_number = var.elasticache_outbound_acl_rules[count.index]["rule_number"]
+  rule_action = var.elasticache_outbound_acl_rules[count.index]["rule_action"]
+  from_port   = var.elasticache_outbound_acl_rules[count.index]["from_port"]
+  to_port     = var.elasticache_outbound_acl_rules[count.index]["to_port"]
+  protocol    = var.elasticache_outbound_acl_rules[count.index]["protocol"]
+  cidr_block  = var.elasticache_outbound_acl_rules[count.index]["cidr_block"]
 }
 
 ##############
@@ -554,34 +764,63 @@ resource "aws_network_acl_rule" "elasticache_outbound" {
 #
 # but then when count of aws_eip.nat.*.id is zero, this would throw a resource not found error on aws_eip.nat.*.id.
 locals {
-  nat_gateway_ips = "${split(",", (var.reuse_nat_ips ? join(",", var.external_nat_ip_ids) : join(",", aws_eip.nat.*.id)))}"
+  nat_gateway_ips = split(
+    ",",
+    var.reuse_nat_ips ? join(",", var.external_nat_ip_ids) : join(",", aws_eip.nat.*.id),
+  )
 }
 
 resource "aws_eip" "nat" {
-  count = "${var.create_vpc && (var.enable_nat_gateway && !var.reuse_nat_ips) ? local.nat_gateway_count : 0}"
+  count = var.create_vpc && var.enable_nat_gateway && false == var.reuse_nat_ips ? local.nat_gateway_count : 0
 
   vpc = true
 
-  tags = "${merge(map("Name", format("%s-%s", var.name, element(var.azs, (var.single_nat_gateway ? 0 : count.index)))), var.tags, var.nat_eip_tags)}"
+  tags = merge(
+    {
+      "Name" = format(
+        "%s-%s",
+        var.name,
+        element(var.azs, var.single_nat_gateway ? 0 : count.index),
+      )
+    },
+    var.tags,
+    var.nat_eip_tags,
+  )
 }
 
 resource "aws_nat_gateway" "this" {
-  count = "${var.create_vpc && var.enable_nat_gateway ? local.nat_gateway_count : 0}"
-
-  allocation_id = "${element(local.nat_gateway_ips, (var.single_nat_gateway ? 0 : count.index))}"
-  subnet_id     = "${element(aws_subnet.public.*.id, (var.single_nat_gateway ? 0 : count.index))}"
-
-  tags = "${merge(map("Name", format("%s-%s", var.name, element(var.azs, (var.single_nat_gateway ? 0 : count.index)))), var.tags, var.nat_gateway_tags)}"
-
-  depends_on = ["aws_internet_gateway.this"]
+  count = var.create_vpc && var.enable_nat_gateway ? local.nat_gateway_count : 0
+
+  allocation_id = element(
+    local.nat_gateway_ips,
+    var.single_nat_gateway ? 0 : count.index,
+  )
+  subnet_id = element(
+    aws_subnet.public.*.id,
+    var.single_nat_gateway ? 0 : count.index,
+  )
+
+  tags = merge(
+    {
+      "Name" = format(
+        "%s-%s",
+        var.name,
+        element(var.azs, var.single_nat_gateway ? 0 : count.index),
+      )
+    },
+    var.tags,
+    var.nat_gateway_tags,
+  )
+
+  depends_on = [aws_internet_gateway.this]
 }
 
 resource "aws_route" "private_nat_gateway" {
-  count = "${var.create_vpc && var.enable_nat_gateway ? local.nat_gateway_count : 0}"
+  count = var.create_vpc && var.enable_nat_gateway ? local.nat_gateway_count : 0
 
-  route_table_id         = "${element(aws_route_table.private.*.id, count.index)}"
+  route_table_id         = element(aws_route_table.private.*.id, count.index)
   destination_cidr_block = "0.0.0.0/0"
-  nat_gateway_id         = "${element(aws_nat_gateway.this.*.id, count.index)}"
+  nat_gateway_id         = element(aws_nat_gateway.this.*.id, count.index)
 
   timeouts {
     create = "5m"
@@ -592,338 +831,381 @@ resource "aws_route" "private_nat_gateway" {
 # VPC Endpoint for S3
 ######################
 data "aws_vpc_endpoint_service" "s3" {
-  count = "${var.create_vpc && var.enable_s3_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_s3_endpoint ? 1 : 0
 
   service = "s3"
 }
 
 resource "aws_vpc_endpoint" "s3" {
-  count = "${var.create_vpc && var.enable_s3_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_s3_endpoint ? 1 : 0
 
-  vpc_id       = "${local.vpc_id}"
-  service_name = "${data.aws_vpc_endpoint_service.s3.service_name}"
+  vpc_id       = local.vpc_id
+  service_name = data.aws_vpc_endpoint_service.s3[0].service_name
 }
 
 resource "aws_vpc_endpoint_route_table_association" "private_s3" {
-  count = "${var.create_vpc && var.enable_s3_endpoint ? local.nat_gateway_count : 0}"
+  count = var.create_vpc && var.enable_s3_endpoint ? local.nat_gateway_count : 0
 
-  vpc_endpoint_id = "${aws_vpc_endpoint.s3.id}"
-  route_table_id  = "${element(aws_route_table.private.*.id, count.index)}"
+  vpc_endpoint_id = aws_vpc_endpoint.s3[0].id
+  route_table_id  = element(aws_route_table.private.*.id, count.index)
 }
 
 resource "aws_vpc_endpoint_route_table_association" "intra_s3" {
-  count = "${var.create_vpc && var.enable_s3_endpoint && length(var.intra_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.enable_s3_endpoint && length(var.intra_subnets) > 0 ? 1 : 0
 
-  vpc_endpoint_id = "${aws_vpc_endpoint.s3.id}"
-  route_table_id  = "${element(aws_route_table.intra.*.id, 0)}"
+  vpc_endpoint_id = aws_vpc_endpoint.s3[0].id
+  route_table_id  = element(aws_route_table.intra.*.id, 0)
 }
 
 resource "aws_vpc_endpoint_route_table_association" "public_s3" {
-  count = "${var.create_vpc && var.enable_s3_endpoint && length(var.public_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.enable_s3_endpoint && length(var.public_subnets) > 0 ? 1 : 0
 
-  vpc_endpoint_id = "${aws_vpc_endpoint.s3.id}"
-  route_table_id  = "${aws_route_table.public.id}"
+  vpc_endpoint_id = aws_vpc_endpoint.s3[0].id
+  route_table_id  = aws_route_table.public[0].id
 }
 
 ############################
 # VPC Endpoint for DynamoDB
 ############################
 data "aws_vpc_endpoint_service" "dynamodb" {
-  count = "${var.create_vpc && var.enable_dynamodb_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_dynamodb_endpoint ? 1 : 0
 
   service = "dynamodb"
 }
 
 resource "aws_vpc_endpoint" "dynamodb" {
-  count = "${var.create_vpc && var.enable_dynamodb_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_dynamodb_endpoint ? 1 : 0
 
-  vpc_id       = "${local.vpc_id}"
-  service_name = "${data.aws_vpc_endpoint_service.dynamodb.service_name}"
+  vpc_id       = local.vpc_id
+  service_name = data.aws_vpc_endpoint_service.dynamodb[0].service_name
 }
 
 resource "aws_vpc_endpoint_route_table_association" "private_dynamodb" {
-  count = "${var.create_vpc && var.enable_dynamodb_endpoint ? local.nat_gateway_count : 0}"
+  count = var.create_vpc && var.enable_dynamodb_endpoint ? local.nat_gateway_count : 0
 
-  vpc_endpoint_id = "${aws_vpc_endpoint.dynamodb.id}"
-  route_table_id  = "${element(aws_route_table.private.*.id, count.index)}"
+  vpc_endpoint_id = aws_vpc_endpoint.dynamodb[0].id
+  route_table_id  = element(aws_route_table.private.*.id, count.index)
 }
 
 resource "aws_vpc_endpoint_route_table_association" "intra_dynamodb" {
-  count = "${var.create_vpc && var.enable_dynamodb_endpoint && length(var.intra_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.enable_dynamodb_endpoint && length(var.intra_subnets) > 0 ? 1 : 0
 
-  vpc_endpoint_id = "${aws_vpc_endpoint.dynamodb.id}"
-  route_table_id  = "${element(aws_route_table.intra.*.id, 0)}"
+  vpc_endpoint_id = aws_vpc_endpoint.dynamodb[0].id
+  route_table_id  = element(aws_route_table.intra.*.id, 0)
 }
 
 resource "aws_vpc_endpoint_route_table_association" "public_dynamodb" {
-  count = "${var.create_vpc && var.enable_dynamodb_endpoint && length(var.public_subnets) > 0 ? 1 : 0}"
+  count = var.create_vpc && var.enable_dynamodb_endpoint && length(var.public_subnets) > 0 ? 1 : 0
 
-  vpc_endpoint_id = "${aws_vpc_endpoint.dynamodb.id}"
-  route_table_id  = "${aws_route_table.public.id}"
+  vpc_endpoint_id = aws_vpc_endpoint.dynamodb[0].id
+  route_table_id  = aws_route_table.public[0].id
 }
 
 #######################
 # VPC Endpoint for SSM
 #######################
 data "aws_vpc_endpoint_service" "ssm" {
-  count = "${var.create_vpc && var.enable_ssm_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ssm_endpoint ? 1 : 0
 
   service = "ssm"
 }
 
 resource "aws_vpc_endpoint" "ssm" {
-  count = "${var.create_vpc && var.enable_ssm_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ssm_endpoint ? 1 : 0
 
-  vpc_id            = "${local.vpc_id}"
-  service_name      = "${data.aws_vpc_endpoint_service.ssm.service_name}"
+  vpc_id            = local.vpc_id
+  service_name      = data.aws_vpc_endpoint_service.ssm[0].service_name
   vpc_endpoint_type = "Interface"
 
-  security_group_ids  = ["${var.ssm_endpoint_security_group_ids}"]
-  subnet_ids          = ["${coalescelist(var.ssm_endpoint_subnet_ids, aws_subnet.private.*.id)}"]
-  private_dns_enabled = "${var.ssm_endpoint_private_dns_enabled}"
+  security_group_ids  = var.ssm_endpoint_security_group_ids
+  subnet_ids          = coalescelist(var.ssm_endpoint_subnet_ids, aws_subnet.private.*.id)
+  private_dns_enabled = var.ssm_endpoint_private_dns_enabled
 }
 
 ###############################
 # VPC Endpoint for SSMMESSAGES
 ###############################
 data "aws_vpc_endpoint_service" "ssmmessages" {
-  count = "${var.create_vpc && var.enable_ssmmessages_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ssmmessages_endpoint ? 1 : 0
 
   service = "ssmmessages"
 }
 
 resource "aws_vpc_endpoint" "ssmmessages" {
-  count = "${var.create_vpc && var.enable_ssmmessages_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ssmmessages_endpoint ? 1 : 0
 
-  vpc_id            = "${local.vpc_id}"
-  service_name      = "${data.aws_vpc_endpoint_service.ssmmessages.service_name}"
+  vpc_id            = local.vpc_id
+  service_name      = data.aws_vpc_endpoint_service.ssmmessages[0].service_name
   vpc_endpoint_type = "Interface"
 
-  security_group_ids  = ["${var.ssmmessages_endpoint_security_group_ids}"]
-  subnet_ids          = ["${coalescelist(var.ssmmessages_endpoint_subnet_ids, aws_subnet.private.*.id)}"]
-  private_dns_enabled = "${var.ssmmessages_endpoint_private_dns_enabled}"
+  security_group_ids  = var.ssmmessages_endpoint_security_group_ids
+  subnet_ids          = coalescelist(var.ssmmessages_endpoint_subnet_ids, aws_subnet.private.*.id)
+  private_dns_enabled = var.ssmmessages_endpoint_private_dns_enabled
 }
 
 #######################
 # VPC Endpoint for EC2
 #######################
 data "aws_vpc_endpoint_service" "ec2" {
-  count = "${var.create_vpc && var.enable_ec2_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ec2_endpoint ? 1 : 0
 
   service = "ec2"
 }
 
 resource "aws_vpc_endpoint" "ec2" {
-  count = "${var.create_vpc && var.enable_ec2_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ec2_endpoint ? 1 : 0
 
-  vpc_id            = "${local.vpc_id}"
-  service_name      = "${data.aws_vpc_endpoint_service.ec2.service_name}"
+  vpc_id            = local.vpc_id
+  service_name      = data.aws_vpc_endpoint_service.ec2[0].service_name
   vpc_endpoint_type = "Interface"
 
-  security_group_ids  = ["${var.ec2_endpoint_security_group_ids}"]
-  subnet_ids          = ["${coalescelist(var.ec2_endpoint_subnet_ids, aws_subnet.private.*.id)}"]
-  private_dns_enabled = "${var.ec2_endpoint_private_dns_enabled}"
+  security_group_ids  = var.ec2_endpoint_security_group_ids
+  subnet_ids          = coalescelist(var.ec2_endpoint_subnet_ids, aws_subnet.private.*.id)
+  private_dns_enabled = var.ec2_endpoint_private_dns_enabled
 }
 
 ###############################
 # VPC Endpoint for EC2MESSAGES
 ###############################
 data "aws_vpc_endpoint_service" "ec2messages" {
-  count = "${var.create_vpc && var.enable_ec2messages_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ec2messages_endpoint ? 1 : 0
 
   service = "ec2messages"
 }
 
 resource "aws_vpc_endpoint" "ec2messages" {
-  count = "${var.create_vpc && var.enable_ec2messages_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ec2messages_endpoint ? 1 : 0
 
-  vpc_id            = "${local.vpc_id}"
-  service_name      = "${data.aws_vpc_endpoint_service.ec2messages.service_name}"
+  vpc_id            = local.vpc_id
+  service_name      = data.aws_vpc_endpoint_service.ec2messages[0].service_name
   vpc_endpoint_type = "Interface"
 
-  security_group_ids  = ["${var.ec2messages_endpoint_security_group_ids}"]
-  subnet_ids          = ["${coalescelist(var.ec2messages_endpoint_subnet_ids, aws_subnet.private.*.id)}"]
-  private_dns_enabled = "${var.ec2messages_endpoint_private_dns_enabled}"
+  security_group_ids  = var.ec2messages_endpoint_security_group_ids
+  subnet_ids          = coalescelist(var.ec2messages_endpoint_subnet_ids, aws_subnet.private.*.id)
+  private_dns_enabled = var.ec2messages_endpoint_private_dns_enabled
 }
 
 ###########################
 # VPC Endpoint for ECR API
 ###########################
 data "aws_vpc_endpoint_service" "ecr_api" {
-  count = "${var.create_vpc && var.enable_ecr_api_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ecr_api_endpoint ? 1 : 0
 
   service = "ecr.api"
 }
 
 resource "aws_vpc_endpoint" "ecr_api" {
-  count = "${var.create_vpc && var.enable_ecr_api_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ecr_api_endpoint ? 1 : 0
 
-  vpc_id            = "${local.vpc_id}"
-  service_name      = "${data.aws_vpc_endpoint_service.ecr_api.service_name}"
+  vpc_id            = local.vpc_id
+  service_name      = data.aws_vpc_endpoint_service.ecr_api[0].service_name
   vpc_endpoint_type = "Interface"
 
-  security_group_ids  = ["${var.ecr_api_endpoint_security_group_ids}"]
-  subnet_ids          = ["${coalescelist(var.ecr_api_endpoint_subnet_ids, aws_subnet.private.*.id)}"]
-  private_dns_enabled = "${var.ecr_api_endpoint_private_dns_enabled}"
+  security_group_ids  = var.ecr_api_endpoint_security_group_ids
+  subnet_ids          = coalescelist(var.ecr_api_endpoint_subnet_ids, aws_subnet.private.*.id)
+  private_dns_enabled = var.ecr_api_endpoint_private_dns_enabled
 }
 
 ###########################
 # VPC Endpoint for ECR DKR
 ###########################
 data "aws_vpc_endpoint_service" "ecr_dkr" {
-  count = "${var.create_vpc && var.enable_ecr_dkr_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ecr_dkr_endpoint ? 1 : 0
 
   service = "ecr.dkr"
 }
 
 resource "aws_vpc_endpoint" "ecr_dkr" {
-  count = "${var.create_vpc && var.enable_ecr_dkr_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_ecr_dkr_endpoint ? 1 : 0
 
-  vpc_id            = "${local.vpc_id}"
-  service_name      = "${data.aws_vpc_endpoint_service.ecr_dkr.service_name}"
+  vpc_id            = local.vpc_id
+  service_name      = data.aws_vpc_endpoint_service.ecr_dkr[0].service_name
   vpc_endpoint_type = "Interface"
 
-  security_group_ids  = ["${var.ecr_dkr_endpoint_security_group_ids}"]
-  subnet_ids          = ["${coalescelist(var.ecr_dkr_endpoint_subnet_ids, aws_subnet.private.*.id)}"]
-  private_dns_enabled = "${var.ecr_dkr_endpoint_private_dns_enabled}"
+  security_group_ids  = var.ecr_dkr_endpoint_security_group_ids
+  subnet_ids          = coalescelist(var.ecr_dkr_endpoint_subnet_ids, aws_subnet.private.*.id)
+  private_dns_enabled = var.ecr_dkr_endpoint_private_dns_enabled
 }
 
 #######################
 # VPC Endpoint for API Gateway
 #######################
 data "aws_vpc_endpoint_service" "apigw" {
-  count = "${var.create_vpc && var.enable_apigw_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_apigw_endpoint ? 1 : 0
 
   service = "execute-api"
 }
 
 resource "aws_vpc_endpoint" "apigw" {
-  count = "${var.create_vpc && var.enable_apigw_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_apigw_endpoint ? 1 : 0
 
-  vpc_id            = "${local.vpc_id}"
-  service_name      = "${data.aws_vpc_endpoint_service.apigw.service_name}"
+  vpc_id            = local.vpc_id
+  service_name      = data.aws_vpc_endpoint_service.apigw[0].service_name
   vpc_endpoint_type = "Interface"
 
-  security_group_ids  = ["${var.apigw_endpoint_security_group_ids}"]
-  subnet_ids          = ["${coalescelist(var.apigw_endpoint_subnet_ids, aws_subnet.private.*.id)}"]
-  private_dns_enabled = "${var.apigw_endpoint_private_dns_enabled}"
+  security_group_ids  = var.apigw_endpoint_security_group_ids
+  subnet_ids          = coalescelist(var.apigw_endpoint_subnet_ids, aws_subnet.private.*.id)
+  private_dns_enabled = var.apigw_endpoint_private_dns_enabled
 }
 
 #######################
 # VPC Endpoint for KMS
 #######################
 data "aws_vpc_endpoint_service" "kms" {
-  count = "${var.create_vpc && var.enable_kms_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_kms_endpoint ? 1 : 0
 
   service = "kms"
 }
 
 resource "aws_vpc_endpoint" "kms" {
-  count = "${var.create_vpc && var.enable_kms_endpoint ? 1 : 0}"
+  count = var.create_vpc && var.enable_kms_endpoint ? 1 : 0
 
-  vpc_id            = "${local.vpc_id}"
-  service_name      = "${data.aws_vpc_endpoint_service.kms.service_name}"
+  vpc_id            = local.vpc_id
+  service_name      = data.aws_vpc_endpoint_service.kms[0].service_name
   vpc_endpoint_type = "Interface"
 
-  security_group_ids  = ["${var.kms_endpoint_security_group_ids}"]
-  subnet_ids          = ["${coalescelist(var.kms_endpoint_subnet_ids, aws_subnet.private.*.id)}"]
-  private_dns_enabled = "${var.kms_endpoint_private_dns_enabled}"
+  security_group_ids  = var.kms_endpoint_security_group_ids
+  subnet_ids          = coalescelist(var.kms_endpoint_subnet_ids, aws_subnet.private.*.id)
+  private_dns_enabled = var.kms_endpoint_private_dns_enabled
 }
 
 ##########################
 # Route table association
 ##########################
 resource "aws_route_table_association" "private" {
-  count = "${var.create_vpc && length(var.private_subnets) > 0 ? length(var.private_subnets) : 0}"
+  count = var.create_vpc && length(var.private_subnets) > 0 ? length(var.private_subnets) : 0
 
-  subnet_id      = "${element(aws_subnet.private.*.id, count.index)}"
-  route_table_id = "${element(aws_route_table.private.*.id, (var.single_nat_gateway ? 0 : count.index))}"
+  subnet_id = element(aws_subnet.private.*.id, count.index)
+  route_table_id = element(
+    aws_route_table.private.*.id,
+    var.single_nat_gateway ? 0 : count.index,
+  )
 }
 
 resource "aws_route_table_association" "database" {
-  count = "${var.create_vpc && length(var.database_subnets) > 0 ? length(var.database_subnets) : 0}"
+  count = var.create_vpc && length(var.database_subnets) > 0 ? length(var.database_subnets) : 0
 
-  subnet_id      = "${element(aws_subnet.database.*.id, count.index)}"
-  route_table_id = "${element(coalescelist(aws_route_table.database.*.id, aws_route_table.private.*.id), (var.single_nat_gateway || var.create_database_subnet_route_table ? 0 : count.index))}"
+  subnet_id = element(aws_subnet.database.*.id, count.index)
+  route_table_id = element(
+    coalescelist(aws_route_table.database.*.id, aws_route_table.private.*.id),
+    var.single_nat_gateway || var.create_database_subnet_route_table ? 0 : count.index,
+  )
 }
 
 resource "aws_route_table_association" "redshift" {
-  count = "${var.create_vpc && length(var.redshift_subnets) > 0 && !var.enable_public_redshift ? length(var.redshift_subnets) : 0}"
+  count = var.create_vpc && length(var.redshift_subnets) > 0 && false == var.enable_public_redshift ? length(var.redshift_subnets) : 0
 
-  subnet_id      = "${element(aws_subnet.redshift.*.id, count.index)}"
-  route_table_id = "${element(coalescelist(aws_route_table.redshift.*.id, aws_route_table.private.*.id), (var.single_nat_gateway || var.create_redshift_subnet_route_table ? 0 : count.index))}"
+  subnet_id = element(aws_subnet.redshift.*.id, count.index)
+  route_table_id = element(
+    coalescelist(aws_route_table.redshift.*.id, aws_route_table.private.*.id),
+    var.single_nat_gateway || var.create_redshift_subnet_route_table ? 0 : count.index,
+  )
 }
 
 resource "aws_route_table_association" "redshift_public" {
-  count = "${var.create_vpc && length(var.redshift_subnets) > 0 && var.enable_public_redshift ? length(var.redshift_subnets) : 0}"
+  count = var.create_vpc && length(var.redshift_subnets) > 0 && var.enable_public_redshift ? length(var.redshift_subnets) : 0
 
-  subnet_id      = "${element(aws_subnet.redshift.*.id, count.index)}"
-  route_table_id = "${element(coalescelist(aws_route_table.redshift.*.id, aws_route_table.public.*.id), (var.single_nat_gateway || var.create_redshift_subnet_route_table ? 0 : count.index))}"
+  subnet_id = element(aws_subnet.redshift.*.id, count.index)
+  route_table_id = element(
+    coalescelist(aws_route_table.redshift.*.id, aws_route_table.public.*.id),
+    var.single_nat_gateway || var.create_redshift_subnet_route_table ? 0 : count.index,
+  )
 }
 
 resource "aws_route_table_association" "elasticache" {
-  count = "${var.create_vpc && length(var.elasticache_subnets) > 0 ? length(var.elasticache_subnets) : 0}"
+  count = var.create_vpc && length(var.elasticache_subnets) > 0 ? length(var.elasticache_subnets) : 0
 
-  subnet_id      = "${element(aws_subnet.elasticache.*.id, count.index)}"
-  route_table_id = "${element(coalescelist(aws_route_table.elasticache.*.id, aws_route_table.private.*.id), (var.single_nat_gateway || var.create_elasticache_subnet_route_table ? 0 : count.index))}"
+  subnet_id = element(aws_subnet.elasticache.*.id, count.index)
+  route_table_id = element(
+    coalescelist(
+      aws_route_table.elasticache.*.id,
+      aws_route_table.private.*.id,
+    ),
+    var.single_nat_gateway || var.create_elasticache_subnet_route_table ? 0 : count.index,
+  )
 }
 
 resource "aws_route_table_association" "intra" {
-  count = "${var.create_vpc && length(var.intra_subnets) > 0 ? length(var.intra_subnets) : 0}"
+  count = var.create_vpc && length(var.intra_subnets) > 0 ? length(var.intra_subnets) : 0
 
-  subnet_id      = "${element(aws_subnet.intra.*.id, count.index)}"
-  route_table_id = "${element(aws_route_table.intra.*.id, 0)}"
+  subnet_id      = element(aws_subnet.intra.*.id, count.index)
+  route_table_id = element(aws_route_table.intra.*.id, 0)
 }
 
 resource "aws_route_table_association" "public" {
-  count = "${var.create_vpc && length(var.public_subnets) > 0 ? length(var.public_subnets) : 0}"
+  count = var.create_vpc && length(var.public_subnets) > 0 ? length(var.public_subnets) : 0
 
-  subnet_id      = "${element(aws_subnet.public.*.id, count.index)}"
-  route_table_id = "${aws_route_table.public.id}"
+  subnet_id      = element(aws_subnet.public.*.id, count.index)
+  route_table_id = aws_route_table.public[0].id
 }
 
 ##############
 # VPN Gateway
 ##############
 resource "aws_vpn_gateway" "this" {
-  count = "${var.create_vpc && var.enable_vpn_gateway ? 1 : 0}"
+  count = var.create_vpc && var.enable_vpn_gateway ? 1 : 0
 
-  vpc_id          = "${local.vpc_id}"
-  amazon_side_asn = "${var.amazon_side_asn}"
+  vpc_id          = local.vpc_id
+  amazon_side_asn = var.amazon_side_asn
 
-  tags = "${merge(map("Name", format("%s", var.name)), var.tags, var.vpn_gateway_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s", var.name)
+    },
+    var.tags,
+    var.vpn_gateway_tags,
+  )
 }
 
 resource "aws_vpn_gateway_attachment" "this" {
-  count = "${var.vpn_gateway_id != "" ? 1 : 0}"
+  count = var.vpn_gateway_id != "" ? 1 : 0
 
-  vpc_id         = "${local.vpc_id}"
-  vpn_gateway_id = "${var.vpn_gateway_id}"
+  vpc_id         = local.vpc_id
+  vpn_gateway_id = var.vpn_gateway_id
 }
 
 resource "aws_vpn_gateway_route_propagation" "public" {
-  count = "${var.create_vpc && var.propagate_public_route_tables_vgw && (var.enable_vpn_gateway || var.vpn_gateway_id != "") ? 1 : 0}"
+  count = var.create_vpc && var.propagate_public_route_tables_vgw && var.enable_vpn_gateway || var.vpn_gateway_id != "" ? 1 : 0
 
-  route_table_id = "${element(aws_route_table.public.*.id, count.index)}"
-  vpn_gateway_id = "${element(concat(aws_vpn_gateway.this.*.id, aws_vpn_gateway_attachment.this.*.vpn_gateway_id), count.index)}"
+  route_table_id = element(aws_route_table.public.*.id, count.index)
+  vpn_gateway_id = element(
+    concat(
+      aws_vpn_gateway.this.*.id,
+      aws_vpn_gateway_attachment.this.*.vpn_gateway_id,
+    ),
+    count.index,
+  )
 }
 
 resource "aws_vpn_gateway_route_propagation" "private" {
-  count = "${var.create_vpc && var.propagate_private_route_tables_vgw && (var.enable_vpn_gateway || var.vpn_gateway_id != "") ? length(var.private_subnets) : 0}"
+  count = var.create_vpc && var.propagate_private_route_tables_vgw && var.enable_vpn_gateway || var.vpn_gateway_id != "" ? length(var.private_subnets) : 0
 
-  route_table_id = "${element(aws_route_table.private.*.id, count.index)}"
-  vpn_gateway_id = "${element(concat(aws_vpn_gateway.this.*.id, aws_vpn_gateway_attachment.this.*.vpn_gateway_id), count.index)}"
+  route_table_id = element(aws_route_table.private.*.id, count.index)
+  vpn_gateway_id = element(
+    concat(
+      aws_vpn_gateway.this.*.id,
+      aws_vpn_gateway_attachment.this.*.vpn_gateway_id,
+    ),
+    count.index,
+  )
 }
 
 ###########
 # Defaults
 ###########
 resource "aws_default_vpc" "this" {
-  count = "${var.manage_default_vpc ? 1 : 0}"
+  count = var.manage_default_vpc ? 1 : 0
 
-  enable_dns_support   = "${var.default_vpc_enable_dns_support}"
-  enable_dns_hostnames = "${var.default_vpc_enable_dns_hostnames}"
-  enable_classiclink   = "${var.default_vpc_enable_classiclink}"
+  enable_dns_support   = var.default_vpc_enable_dns_support
+  enable_dns_hostnames = var.default_vpc_enable_dns_hostnames
+  enable_classiclink   = var.default_vpc_enable_classiclink
 
-  tags = "${merge(map("Name", format("%s", var.default_vpc_name)), var.tags, var.default_vpc_tags)}"
+  tags = merge(
+    {
+      "Name" = format("%s", var.default_vpc_name)
+    },
+    var.tags,
+    var.default_vpc_tags,
+  )
 }
+
diff --git a/outputs.tf b/outputs.tf
index 425af581e..304501b32 100644
--- a/outputs.tf
+++ b/outputs.tf
@@ -1,46 +1,46 @@
 output "vpc_id" {
   description = "The ID of the VPC"
-  value       = "${element(concat(aws_vpc.this.*.id, list("")), 0)}"
+  value       = element(concat(aws_vpc.this.*.id, [""]), 0)
 }
 
 output "vpc_arn" {
   description = "The ARN of the VPC"
-  value       = "${element(concat(aws_vpc.this.*.arn, list("")), 0)}"
+  value       = element(concat(aws_vpc.this.*.arn, [""]), 0)
 }
 
 output "vpc_cidr_block" {
   description = "The CIDR block of the VPC"
-  value       = "${element(concat(aws_vpc.this.*.cidr_block, list("")), 0)}"
+  value       = element(concat(aws_vpc.this.*.cidr_block, [""]), 0)
 }
 
 output "default_security_group_id" {
   description = "The ID of the security group created by default on VPC creation"
-  value       = "${element(concat(aws_vpc.this.*.default_security_group_id, list("")), 0)}"
+  value       = element(concat(aws_vpc.this.*.default_security_group_id, [""]), 0)
 }
 
 output "default_network_acl_id" {
   description = "The ID of the default network ACL"
-  value       = "${element(concat(aws_vpc.this.*.default_network_acl_id, list("")), 0)}"
+  value       = element(concat(aws_vpc.this.*.default_network_acl_id, [""]), 0)
 }
 
 output "default_route_table_id" {
   description = "The ID of the default route table"
-  value       = "${element(concat(aws_vpc.this.*.default_route_table_id, list("")), 0)}"
+  value       = element(concat(aws_vpc.this.*.default_route_table_id, [""]), 0)
 }
 
 output "vpc_instance_tenancy" {
   description = "Tenancy of instances spin up within VPC"
-  value       = "${element(concat(aws_vpc.this.*.instance_tenancy, list("")), 0)}"
+  value       = element(concat(aws_vpc.this.*.instance_tenancy, [""]), 0)
 }
 
 output "vpc_enable_dns_support" {
   description = "Whether or not the VPC has DNS support"
-  value       = "${element(concat(aws_vpc.this.*.enable_dns_support, list("")), 0)}"
+  value       = element(concat(aws_vpc.this.*.enable_dns_support, [""]), 0)
 }
 
 output "vpc_enable_dns_hostnames" {
   description = "Whether or not the VPC has DNS hostname support"
-  value       = "${element(concat(aws_vpc.this.*.enable_dns_hostnames, list("")), 0)}"
+  value       = element(concat(aws_vpc.this.*.enable_dns_hostnames, [""]), 0)
 }
 
 //output "vpc_enable_classiclink" {
@@ -50,7 +50,7 @@ output "vpc_enable_dns_hostnames" {
 
 output "vpc_main_route_table_id" {
   description = "The ID of the main route table associated with this VPC"
-  value       = "${element(concat(aws_vpc.this.*.main_route_table_id, list("")), 0)}"
+  value       = element(concat(aws_vpc.this.*.main_route_table_id, [""]), 0)
 }
 
 //output "vpc_ipv6_association_id" {
@@ -65,212 +65,234 @@ output "vpc_main_route_table_id" {
 
 output "vpc_secondary_cidr_blocks" {
   description = "List of secondary CIDR blocks of the VPC"
-  value       = ["${aws_vpc_ipv4_cidr_block_association.this.*.cidr_block}"]
+  value       = aws_vpc_ipv4_cidr_block_association.this.*.cidr_block
 }
 
 output "private_subnets" {
   description = "List of IDs of private subnets"
-  value       = ["${aws_subnet.private.*.id}"]
+  value       = aws_subnet.private.*.id
 }
 
 output "private_subnet_arns" {
   description = "List of ARNs of private subnets"
-  value       = ["${aws_subnet.private.*.arn}"]
+  value       = aws_subnet.private.*.arn
 }
 
 output "private_subnets_cidr_blocks" {
   description = "List of cidr_blocks of private subnets"
-  value       = ["${aws_subnet.private.*.cidr_block}"]
+  value       = aws_subnet.private.*.cidr_block
 }
 
 output "public_subnets" {
   description = "List of IDs of public subnets"
-  value       = ["${aws_subnet.public.*.id}"]
+  value       = aws_subnet.public.*.id
 }
 
 output "public_subnet_arns" {
   description = "List of ARNs of public subnets"
-  value       = ["${aws_subnet.public.*.arn}"]
+  value       = aws_subnet.public.*.arn
 }
 
 output "public_subnets_cidr_blocks" {
   description = "List of cidr_blocks of public subnets"
-  value       = ["${aws_subnet.public.*.cidr_block}"]
+  value       = aws_subnet.public.*.cidr_block
 }
 
 output "database_subnets" {
   description = "List of IDs of database subnets"
-  value       = ["${aws_subnet.database.*.id}"]
+  value       = aws_subnet.database.*.id
 }
 
 output "database_subnet_arns" {
   description = "List of ARNs of database subnets"
-  value       = ["${aws_subnet.database.*.arn}"]
+  value       = aws_subnet.database.*.arn
 }
 
 output "database_subnets_cidr_blocks" {
   description = "List of cidr_blocks of database subnets"
-  value       = ["${aws_subnet.database.*.cidr_block}"]
+  value       = aws_subnet.database.*.cidr_block
 }
 
 output "database_subnet_group" {
   description = "ID of database subnet group"
-  value       = "${element(concat(aws_db_subnet_group.database.*.id, list("")), 0)}"
+  value       = element(concat(aws_db_subnet_group.database.*.id, [""]), 0)
 }
 
 output "redshift_subnets" {
   description = "List of IDs of redshift subnets"
-  value       = ["${aws_subnet.redshift.*.id}"]
+  value       = aws_subnet.redshift.*.id
 }
 
 output "redshift_subnet_arns" {
   description = "List of ARNs of redshift subnets"
-  value       = ["${aws_subnet.redshift.*.arn}"]
+  value       = aws_subnet.redshift.*.arn
 }
 
 output "redshift_subnets_cidr_blocks" {
   description = "List of cidr_blocks of redshift subnets"
-  value       = ["${aws_subnet.redshift.*.cidr_block}"]
+  value       = aws_subnet.redshift.*.cidr_block
 }
 
 output "redshift_subnet_group" {
   description = "ID of redshift subnet group"
-  value       = "${element(concat(aws_redshift_subnet_group.redshift.*.id, list("")), 0)}"
+  value       = element(concat(aws_redshift_subnet_group.redshift.*.id, [""]), 0)
 }
 
 output "elasticache_subnets" {
   description = "List of IDs of elasticache subnets"
-  value       = ["${aws_subnet.elasticache.*.id}"]
+  value       = aws_subnet.elasticache.*.id
 }
 
 output "elasticache_subnet_arns" {
   description = "List of ARNs of elasticache subnets"
-  value       = ["${aws_subnet.elasticache.*.arn}"]
+  value       = aws_subnet.elasticache.*.arn
 }
 
 output "elasticache_subnets_cidr_blocks" {
   description = "List of cidr_blocks of elasticache subnets"
-  value       = ["${aws_subnet.elasticache.*.cidr_block}"]
+  value       = aws_subnet.elasticache.*.cidr_block
 }
 
 output "intra_subnets" {
   description = "List of IDs of intra subnets"
-  value       = ["${aws_subnet.intra.*.id}"]
+  value       = aws_subnet.intra.*.id
 }
 
 output "intra_subnet_arns" {
   description = "List of ARNs of intra subnets"
-  value       = ["${aws_subnet.intra.*.arn}"]
+  value       = aws_subnet.intra.*.arn
 }
 
 output "intra_subnets_cidr_blocks" {
   description = "List of cidr_blocks of intra subnets"
-  value       = ["${aws_subnet.intra.*.cidr_block}"]
+  value       = aws_subnet.intra.*.cidr_block
 }
 
 output "elasticache_subnet_group" {
   description = "ID of elasticache subnet group"
-  value       = "${element(concat(aws_elasticache_subnet_group.elasticache.*.id, list("")), 0)}"
+  value = element(
+    concat(aws_elasticache_subnet_group.elasticache.*.id, [""]),
+    0,
+  )
 }
 
 output "elasticache_subnet_group_name" {
   description = "Name of elasticache subnet group"
-  value       = "${element(concat(aws_elasticache_subnet_group.elasticache.*.name, list("")), 0)}"
+  value = element(
+    concat(aws_elasticache_subnet_group.elasticache.*.name, [""]),
+    0,
+  )
 }
 
 output "public_route_table_ids" {
   description = "List of IDs of public route tables"
-  value       = ["${aws_route_table.public.*.id}"]
+  value       = aws_route_table.public.*.id
 }
 
 output "private_route_table_ids" {
   description = "List of IDs of private route tables"
-  value       = ["${aws_route_table.private.*.id}"]
+  value       = aws_route_table.private.*.id
 }
 
 output "database_route_table_ids" {
   description = "List of IDs of database route tables"
-  value       = ["${coalescelist(aws_route_table.database.*.id, aws_route_table.private.*.id)}"]
+  value       = length(aws_route_table.database.*.id) > 0 ? aws_route_table.database.*.id : aws_route_table.private.*.id
 }
 
 output "redshift_route_table_ids" {
   description = "List of IDs of redshift route tables"
-  value       = ["${coalescelist(aws_route_table.redshift.*.id, aws_route_table.private.*.id)}"]
+  value       = length(aws_route_table.redshift.*.id) > 0 ? aws_route_table.redshift.*.id : aws_route_table.private.*.id
 }
 
 output "elasticache_route_table_ids" {
   description = "List of IDs of elasticache route tables"
-  value       = ["${coalescelist(aws_route_table.elasticache.*.id, aws_route_table.private.*.id)}"]
+  value       = length(aws_route_table.elasticache.*.id) > 0 ? aws_route_table.elasticache.*.id : aws_route_table.private.*.id
 }
 
 output "intra_route_table_ids" {
   description = "List of IDs of intra route tables"
-  value       = ["${aws_route_table.intra.*.id}"]
+  value       = aws_route_table.intra.*.id
 }
 
 output "nat_ids" {
   description = "List of allocation ID of Elastic IPs created for AWS NAT Gateway"
-  value       = ["${aws_eip.nat.*.id}"]
+  value       = aws_eip.nat.*.id
 }
 
 output "nat_public_ips" {
   description = "List of public Elastic IPs created for AWS NAT Gateway"
-  value       = ["${aws_eip.nat.*.public_ip}"]
+  value       = aws_eip.nat.*.public_ip
 }
 
 output "natgw_ids" {
   description = "List of NAT Gateway IDs"
-  value       = ["${aws_nat_gateway.this.*.id}"]
+  value       = aws_nat_gateway.this.*.id
 }
 
 output "igw_id" {
   description = "The ID of the Internet Gateway"
-  value       = "${element(concat(aws_internet_gateway.this.*.id, list("")), 0)}"
+  value       = element(concat(aws_internet_gateway.this.*.id, [""]), 0)
 }
 
 output "vgw_id" {
   description = "The ID of the VPN Gateway"
-  value       = "${element(concat(aws_vpn_gateway.this.*.id, aws_vpn_gateway_attachment.this.*.vpn_gateway_id, list("")), 0)}"
+  value = element(
+    concat(
+      aws_vpn_gateway.this.*.id,
+      aws_vpn_gateway_attachment.this.*.vpn_gateway_id,
+      [""],
+    ),
+    0,
+  )
 }
 
 output "default_vpc_id" {
   description = "The ID of the VPC"
-  value       = "${element(concat(aws_default_vpc.this.*.id, list("")), 0)}"
+  value       = element(concat(aws_default_vpc.this.*.id, [""]), 0)
 }
 
 output "default_vpc_cidr_block" {
   description = "The CIDR block of the VPC"
-  value       = "${element(concat(aws_default_vpc.this.*.cidr_block, list("")), 0)}"
+  value       = element(concat(aws_default_vpc.this.*.cidr_block, [""]), 0)
 }
 
 output "default_vpc_default_security_group_id" {
   description = "The ID of the security group created by default on VPC creation"
-  value       = "${element(concat(aws_default_vpc.this.*.default_security_group_id, list("")), 0)}"
+  value = element(
+    concat(aws_default_vpc.this.*.default_security_group_id, [""]),
+    0,
+  )
 }
 
 output "default_vpc_default_network_acl_id" {
   description = "The ID of the default network ACL"
-  value       = "${element(concat(aws_default_vpc.this.*.default_network_acl_id, list("")), 0)}"
+  value = element(
+    concat(aws_default_vpc.this.*.default_network_acl_id, [""]),
+    0,
+  )
 }
 
 output "default_vpc_default_route_table_id" {
   description = "The ID of the default route table"
-  value       = "${element(concat(aws_default_vpc.this.*.default_route_table_id, list("")), 0)}"
+  value = element(
+    concat(aws_default_vpc.this.*.default_route_table_id, [""]),
+    0,
+  )
 }
 
 output "default_vpc_instance_tenancy" {
   description = "Tenancy of instances spin up within VPC"
-  value       = "${element(concat(aws_default_vpc.this.*.instance_tenancy, list("")), 0)}"
+  value       = element(concat(aws_default_vpc.this.*.instance_tenancy, [""]), 0)
 }
 
 output "default_vpc_enable_dns_support" {
   description = "Whether or not the VPC has DNS support"
-  value       = "${element(concat(aws_default_vpc.this.*.enable_dns_support, list("")), 0)}"
+  value       = element(concat(aws_default_vpc.this.*.enable_dns_support, [""]), 0)
 }
 
 output "default_vpc_enable_dns_hostnames" {
   description = "Whether or not the VPC has DNS hostname support"
-  value       = "${element(concat(aws_default_vpc.this.*.enable_dns_hostnames, list("")), 0)}"
+  value       = element(concat(aws_default_vpc.this.*.enable_dns_hostnames, [""]), 0)
 }
 
 //output "default_vpc_enable_classiclink" {
@@ -280,7 +302,7 @@ output "default_vpc_enable_dns_hostnames" {
 
 output "default_vpc_main_route_table_id" {
   description = "The ID of the main route table associated with this VPC"
-  value       = "${element(concat(aws_default_vpc.this.*.main_route_table_id, list("")), 0)}"
+  value       = element(concat(aws_default_vpc.this.*.main_route_table_id, [""]), 0)
 }
 
 //output "default_vpc_ipv6_association_id" {
@@ -295,177 +317,178 @@ output "default_vpc_main_route_table_id" {
 
 output "public_network_acl_id" {
   description = "ID of the public network ACL"
-  value       = "${element(concat(aws_network_acl.public.*.id, list("")), 0)}"
+  value       = element(concat(aws_network_acl.public.*.id, [""]), 0)
 }
 
 output "private_network_acl_id" {
   description = "ID of the private network ACL"
-  value       = "${element(concat(aws_network_acl.private.*.id, list("")), 0)}"
+  value       = element(concat(aws_network_acl.private.*.id, [""]), 0)
 }
 
 output "intra_network_acl_id" {
   description = "ID of the intra network ACL"
-  value       = "${element(concat(aws_network_acl.intra.*.id, list("")), 0)}"
+  value       = element(concat(aws_network_acl.intra.*.id, [""]), 0)
 }
 
 output "database_network_acl_id" {
   description = "ID of the database network ACL"
-  value       = "${element(concat(aws_network_acl.database.*.id, list("")), 0)}"
+  value       = element(concat(aws_network_acl.database.*.id, [""]), 0)
 }
 
 output "redshift_network_acl_id" {
   description = "ID of the redshift network ACL"
-  value       = "${element(concat(aws_network_acl.redshift.*.id, list("")), 0)}"
+  value       = element(concat(aws_network_acl.redshift.*.id, [""]), 0)
 }
 
 output "elasticache_network_acl_id" {
   description = "ID of the elasticache network ACL"
-  value       = "${element(concat(aws_network_acl.elasticache.*.id, list("")), 0)}"
+  value       = element(concat(aws_network_acl.elasticache.*.id, [""]), 0)
 }
 
 # VPC Endpoints
 output "vpc_endpoint_s3_id" {
   description = "The ID of VPC endpoint for S3"
-  value       = "${element(concat(aws_vpc_endpoint.s3.*.id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.s3.*.id, [""]), 0)
 }
 
 output "vpc_endpoint_s3_pl_id" {
   description = "The prefix list for the S3 VPC endpoint."
-  value       = "${element(concat(aws_vpc_endpoint.s3.*.prefix_list_id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.s3.*.prefix_list_id, [""]), 0)
 }
 
 output "vpc_endpoint_dynamodb_id" {
   description = "The ID of VPC endpoint for DynamoDB"
-  value       = "${element(concat(aws_vpc_endpoint.dynamodb.*.id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.dynamodb.*.id, [""]), 0)
 }
 
 output "vpc_endpoint_dynamodb_pl_id" {
   description = "The prefix list for the DynamoDB VPC endpoint."
-  value       = "${element(concat(aws_vpc_endpoint.dynamodb.*.prefix_list_id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.dynamodb.*.prefix_list_id, [""]), 0)
 }
 
 output "vpc_endpoint_ssm_id" {
   description = "The ID of VPC endpoint for SSM"
-  value       = "${element(concat(aws_vpc_endpoint.ssm.*.id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.ssm.*.id, [""]), 0)
 }
 
 output "vpc_endpoint_ssm_network_interface_ids" {
   description = "One or more network interfaces for the VPC Endpoint for SSM."
-  value       = "${flatten(aws_vpc_endpoint.ssm.*.network_interface_ids)}"
+  value       = flatten(aws_vpc_endpoint.ssm.*.network_interface_ids)
 }
 
 output "vpc_endpoint_ssm_dns_entry" {
   description = "The DNS entries for the VPC Endpoint for SSM."
-  value       = "${flatten(aws_vpc_endpoint.ssm.*.dns_entry)}"
+  value       = flatten(aws_vpc_endpoint.ssm.*.dns_entry)
 }
 
 output "vpc_endpoint_ssmmessages_id" {
   description = "The ID of VPC endpoint for SSMMESSAGES"
-  value       = "${element(concat(aws_vpc_endpoint.ssmmessages.*.id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.ssmmessages.*.id, [""]), 0)
 }
 
 output "vpc_endpoint_ssmmessages_network_interface_ids" {
   description = "One or more network interfaces for the VPC Endpoint for SSMMESSAGES."
-  value       = "${flatten(aws_vpc_endpoint.ssmmessages.*.network_interface_ids)}"
+  value       = flatten(aws_vpc_endpoint.ssmmessages.*.network_interface_ids)
 }
 
 output "vpc_endpoint_ssmmessages_dns_entry" {
   description = "The DNS entries for the VPC Endpoint for SSMMESSAGES."
-  value       = "${flatten(aws_vpc_endpoint.ssmmessages.*.dns_entry)}"
+  value       = flatten(aws_vpc_endpoint.ssmmessages.*.dns_entry)
 }
 
 output "vpc_endpoint_ec2_id" {
   description = "The ID of VPC endpoint for EC2"
-  value       = "${element(concat(aws_vpc_endpoint.ec2.*.id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.ec2.*.id, [""]), 0)
 }
 
 output "vpc_endpoint_ec2_network_interface_ids" {
   description = "One or more network interfaces for the VPC Endpoint for EC2"
-  value       = "${flatten(aws_vpc_endpoint.ec2.*.network_interface_ids)}"
+  value       = flatten(aws_vpc_endpoint.ec2.*.network_interface_ids)
 }
 
 output "vpc_endpoint_ec2_dns_entry" {
   description = "The DNS entries for the VPC Endpoint for EC2."
-  value       = "${flatten(aws_vpc_endpoint.ec2.*.dns_entry)}"
+  value       = flatten(aws_vpc_endpoint.ec2.*.dns_entry)
 }
 
 output "vpc_endpoint_ec2messages_id" {
   description = "The ID of VPC endpoint for EC2MESSAGES"
-  value       = "${element(concat(aws_vpc_endpoint.ec2messages.*.id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.ec2messages.*.id, [""]), 0)
 }
 
 output "vpc_endpoint_ec2messages_network_interface_ids" {
   description = "One or more network interfaces for the VPC Endpoint for EC2MESSAGES"
-  value       = "${flatten(aws_vpc_endpoint.ec2messages.*.network_interface_ids)}"
+  value       = flatten(aws_vpc_endpoint.ec2messages.*.network_interface_ids)
 }
 
 output "vpc_endpoint_ec2messages_dns_entry" {
   description = "The DNS entries for the VPC Endpoint for EC2MESSAGES."
-  value       = "${flatten(aws_vpc_endpoint.ec2messages.*.dns_entry)}"
+  value       = flatten(aws_vpc_endpoint.ec2messages.*.dns_entry)
 }
 
 output "vpc_endpoint_kms_id" {
   description = "The ID of VPC endpoint for KMS"
-  value       = "${element(concat(aws_vpc_endpoint.kms.*.id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.kms.*.id, [""]), 0)
 }
 
 output "vpc_endpoint_kms_network_interface_ids" {
   description = "One or more network interfaces for the VPC Endpoint for KMS."
-  value       = "${flatten(aws_vpc_endpoint.kms.*.network_interface_ids)}"
+  value       = flatten(aws_vpc_endpoint.kms.*.network_interface_ids)
 }
 
 output "vpc_endpoint_kms_dns_entry" {
   description = "The DNS entries for the VPC Endpoint for KMS."
-  value       = "${flatten(aws_vpc_endpoint.kms.*.dns_entry)}"
+  value       = flatten(aws_vpc_endpoint.kms.*.dns_entry)
 }
 
 output "vpc_endpoint_ecr_api_id" {
   description = "The ID of VPC endpoint for ECR API"
-  value       = "${element(concat(aws_vpc_endpoint.ecr_api.*.id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.ecr_api.*.id, [""]), 0)
 }
 
 output "vpc_endpoint_ecr_api_network_interface_ids" {
   description = "One or more network interfaces for the VPC Endpoint for ECR API."
-  value       = "${flatten(aws_vpc_endpoint.ecr_api.*.network_interface_ids)}"
+  value       = flatten(aws_vpc_endpoint.ecr_api.*.network_interface_ids)
 }
 
 output "vpc_endpoint_ecr_api_dns_entry" {
   description = "The DNS entries for the VPC Endpoint for ECR API."
-  value       = "${flatten(aws_vpc_endpoint.ecr_api.*.dns_entry)}"
+  value       = flatten(aws_vpc_endpoint.ecr_api.*.dns_entry)
 }
 
 output "vpc_endpoint_ecr_dkr_id" {
   description = "The ID of VPC endpoint for ECR DKR"
-  value       = "${element(concat(aws_vpc_endpoint.ecr_dkr.*.id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.ecr_dkr.*.id, [""]), 0)
 }
 
 output "vpc_endpoint_ecr_dkr_network_interface_ids" {
   description = "One or more network interfaces for the VPC Endpoint for ECR DKR."
-  value       = "${flatten(aws_vpc_endpoint.ecr_dkr.*.network_interface_ids)}"
+  value       = flatten(aws_vpc_endpoint.ecr_dkr.*.network_interface_ids)
 }
 
 output "vpc_endpoint_ecr_dkr_dns_entry" {
   description = "The DNS entries for the VPC Endpoint for ECR DKR."
-  value       = "${flatten(aws_vpc_endpoint.ecr_dkr.*.dns_entry)}"
+  value       = flatten(aws_vpc_endpoint.ecr_dkr.*.dns_entry)
 }
 
 output "vpc_endpoint_apigw_id" {
   description = "The ID of VPC endpoint for APIGW"
-  value       = "${element(concat(aws_vpc_endpoint.apigw.*.id, list("")), 0)}"
+  value       = element(concat(aws_vpc_endpoint.apigw.*.id, [""]), 0)
 }
 
 output "vpc_endpoint_apigw_network_interface_ids" {
   description = "One or more network interfaces for the VPC Endpoint for APIGW."
-  value       = "${flatten(aws_vpc_endpoint.apigw.*.network_interface_ids)}"
+  value       = flatten(aws_vpc_endpoint.apigw.*.network_interface_ids)
 }
 
 output "vpc_endpoint_apigw_dns_entry" {
   description = "The DNS entries for the VPC Endpoint for APIGW."
-  value       = "${flatten(aws_vpc_endpoint.apigw.*.dns_entry)}"
+  value       = flatten(aws_vpc_endpoint.apigw.*.dns_entry)
 }
 
 # Static values (arguments)
 output "azs" {
   description = "A list of availability zones specified as argument to this module"
-  value       = "${var.azs}"
+  value       = var.azs
 }
+
diff --git a/variables.tf b/variables.tf
index 33b79d6c5..471e37b1e 100644
--- a/variables.tf
+++ b/variables.tf
@@ -1,5 +1,6 @@
 variable "create_vpc" {
   description = "Controls if VPC should be created (it affects almost all resources)"
+  type        = bool
   default     = true
 }
 
@@ -15,342 +16,409 @@ variable "cidr" {
 
 variable "assign_generated_ipv6_cidr_block" {
   description = "Requests an Amazon-provided IPv6 CIDR block with a /56 prefix length for the VPC. You cannot specify the range of IP addresses, or the size of the CIDR block"
+  type        = bool
   default     = false
 }
 
 variable "secondary_cidr_blocks" {
   description = "List of secondary CIDR blocks to associate with the VPC to extend the IP Address pool"
+  type        = list(string)
   default     = []
 }
 
 variable "instance_tenancy" {
   description = "A tenancy option for instances launched into the VPC"
+  type        = string
   default     = "default"
 }
 
 variable "public_subnet_suffix" {
   description = "Suffix to append to public subnets name"
+  type        = string
   default     = "public"
 }
 
 variable "private_subnet_suffix" {
   description = "Suffix to append to private subnets name"
+  type        = string
   default     = "private"
 }
 
 variable "intra_subnet_suffix" {
   description = "Suffix to append to intra subnets name"
+  type        = string
   default     = "intra"
 }
 
 variable "database_subnet_suffix" {
   description = "Suffix to append to database subnets name"
+  type        = string
   default     = "db"
 }
 
 variable "redshift_subnet_suffix" {
   description = "Suffix to append to redshift subnets name"
+  type        = string
   default     = "redshift"
 }
 
 variable "elasticache_subnet_suffix" {
   description = "Suffix to append to elasticache subnets name"
+  type        = string
   default     = "elasticache"
 }
 
 variable "public_subnets" {
   description = "A list of public subnets inside the VPC"
+  type        = list(string)
   default     = []
 }
 
 variable "private_subnets" {
   description = "A list of private subnets inside the VPC"
+  type        = list(string)
   default     = []
 }
 
 variable "database_subnets" {
   description = "A list of database subnets"
+  type        = list(string)
   default     = []
 }
 
 variable "redshift_subnets" {
   description = "A list of redshift subnets"
+  type        = list(string)
   default     = []
 }
 
 variable "elasticache_subnets" {
   description = "A list of elasticache subnets"
+  type        = list(string)
   default     = []
 }
 
 variable "intra_subnets" {
   description = "A list of intra subnets"
+  type        = list(string)
   default     = []
 }
 
 variable "create_database_subnet_route_table" {
   description = "Controls if separate route table for database should be created"
+  type        = bool
   default     = false
 }
 
 variable "create_redshift_subnet_route_table" {
   description = "Controls if separate route table for redshift should be created"
+  type        = bool
   default     = false
 }
 
 variable "enable_public_redshift" {
   description = "Controls if redshift should have public routing table"
+  type        = bool
   default     = false
 }
 
 variable "create_elasticache_subnet_route_table" {
   description = "Controls if separate route table for elasticache should be created"
+  type        = bool
   default     = false
 }
 
 variable "create_database_subnet_group" {
   description = "Controls if database subnet group should be created"
+  type        = bool
   default     = true
 }
 
 variable "create_elasticache_subnet_group" {
   description = "Controls if elasticache subnet group should be created"
+  type        = bool
   default     = true
 }
 
 variable "create_redshift_subnet_group" {
   description = "Controls if redshift subnet group should be created"
+  type        = bool
   default     = true
 }
 
 variable "create_database_internet_gateway_route" {
   description = "Controls if an internet gateway route for public database access should be created"
+  type        = bool
   default     = false
 }
 
 variable "create_database_nat_gateway_route" {
   description = "Controls if a nat gateway route should be created to give internet access to the database subnets"
+  type        = bool
   default     = false
 }
 
 variable "azs" {
   description = "A list of availability zones in the region"
+  type        = list(string)
   default     = []
 }
 
 variable "enable_dns_hostnames" {
   description = "Should be true to enable DNS hostnames in the VPC"
+  type        = bool
   default     = false
 }
 
 variable "enable_dns_support" {
   description = "Should be true to enable DNS support in the VPC"
+  type        = bool
   default     = true
 }
 
 variable "enable_nat_gateway" {
   description = "Should be true if you want to provision NAT Gateways for each of your private networks"
+  type        = bool
   default     = false
 }
 
 variable "single_nat_gateway" {
   description = "Should be true if you want to provision a single shared NAT Gateway across all of your private networks"
+  type        = bool
   default     = false
 }
 
 variable "one_nat_gateway_per_az" {
   description = "Should be true if you want only one NAT Gateway per availability zone. Requires `var.azs` to be set, and the number of `public_subnets` created to be greater than or equal to the number of availability zones specified in `var.azs`."
+  type        = bool
   default     = false
 }
 
 variable "reuse_nat_ips" {
   description = "Should be true if you don't want EIPs to be created for your NAT Gateways and will instead pass them in via the 'external_nat_ip_ids' variable"
+  type        = bool
   default     = false
 }
 
 variable "external_nat_ip_ids" {
   description = "List of EIP IDs to be assigned to the NAT Gateways (used in combination with reuse_nat_ips)"
-
-  default = []
+  type        = list(string)
+  default     = []
 }
 
 variable "enable_dynamodb_endpoint" {
   description = "Should be true if you want to provision a DynamoDB endpoint to the VPC"
+  type        = bool
   default     = false
 }
 
 variable "enable_s3_endpoint" {
   description = "Should be true if you want to provision an S3 endpoint to the VPC"
+  type        = bool
   default     = false
 }
 
 variable "enable_ssm_endpoint" {
   description = "Should be true if you want to provision an SSM endpoint to the VPC"
+  type        = bool
   default     = false
 }
 
 variable "ssm_endpoint_security_group_ids" {
   description = "The ID of one or more security groups to associate with the network interface for SSM endpoint"
+  type        = list(string)
   default     = []
 }
 
 variable "ssm_endpoint_subnet_ids" {
   description = "The ID of one or more subnets in which to create a network interface for SSM endpoint. Only a single subnet within an AZ is supported. If omitted, private subnets will be used."
+  type        = list(string)
   default     = []
 }
 
 variable "ssm_endpoint_private_dns_enabled" {
   description = "Whether or not to associate a private hosted zone with the specified VPC for SSM endpoint"
+  type        = bool
   default     = false
 }
 
 variable "enable_ssmmessages_endpoint" {
   description = "Should be true if you want to provision a SSMMESSAGES endpoint to the VPC"
+  type        = bool
   default     = false
 }
 
 variable "enable_apigw_endpoint" {
   description = "Should be true if you want to provision an api gateway endpoint to the VPC"
+  type        = bool
   default     = false
 }
 
 variable "apigw_endpoint_security_group_ids" {
   description = "The ID of one or more security groups to associate with the network interface for API GW  endpoint"
+  type        = list(string)
   default     = []
 }
 
 variable "apigw_endpoint_private_dns_enabled" {
   description = "Whether or not to associate a private hosted zone with the specified VPC for API GW endpoint"
+  type        = bool
   default     = false
 }
 
 variable "apigw_endpoint_subnet_ids" {
   description = "The ID of one or more subnets in which to create a network interface for API GW endpoint. Only a single subnet within an AZ is supported. If omitted, private subnets will be used."
+  type        = list(string)
   default     = []
 }
 
 variable "ssmmessages_endpoint_security_group_ids" {
   description = "The ID of one or more security groups to associate with the network interface for SSMMESSAGES endpoint"
+  type        = list(string)
   default     = []
 }
 
 variable "ssmmessages_endpoint_subnet_ids" {
   description = "The ID of one or more subnets in which to create a network interface for SSMMESSAGES endpoint. Only a single subnet within an AZ is supported. If omitted, private subnets will be used."
+  type        = list(string)
   default     = []
 }
 
 variable "ssmmessages_endpoint_private_dns_enabled" {
   description = "Whether or not to associate a private hosted zone with the specified VPC for SSMMESSAGES endpoint"
+  type        = bool
   default     = false
 }
 
 variable "enable_ec2_endpoint" {
   description = "Should be true if you want to provision an EC2 endpoint to the VPC"
+  type        = bool
   default     = false
 }
 
 variable "ec2_endpoint_security_group_ids" {
   description = "The ID of one or more security groups to associate with the network interface for EC2 endpoint"
+  type        = list(string)
   default     = []
 }
 
 variable "ec2_endpoint_private_dns_enabled" {
   description = "Whether or not to associate a private hosted zone with the specified VPC for EC2 endpoint"
+  type        = bool
   default     = false
 }
 
 variable "ec2_endpoint_subnet_ids" {
   description = "The ID of one or more subnets in which to create a network interface for EC2 endpoint. Only a single subnet within an AZ is supported. If omitted, private subnets will be used."
+  type        = list(string)
   default     = []
 }
 
 variable "enable_ec2messages_endpoint" {
   description = "Should be true if you want to provision an EC2MESSAGES endpoint to the VPC"
+  type        = bool
   default     = false
 }
 
 variable "ec2messages_endpoint_security_group_ids" {
   description = "The ID of one or more security groups to associate with the network interface for EC2MESSAGES endpoint"
+  type        = list(string)
   default     = []
 }
 
 variable "ec2messages_endpoint_private_dns_enabled" {
   description = "Whether or not to associate a private hosted zone with the specified VPC for EC2MESSAGES endpoint"
+  type        = bool
   default     = false
 }
 
 variable "ec2messages_endpoint_subnet_ids" {
   description = "The ID of one or more subnets in which to create a network interface for EC2MESSAGES endpoint. Only a single subnet within an AZ is supported. If omitted, private subnets will be used."
+  type        = list(string)
   default     = []
 }
 
 variable "enable_ecr_api_endpoint" {
   description = "Should be true if you want to provision an ecr api endpoint to the VPC"
+  type        = bool
   default     = false
 }
 
 variable "ecr_api_endpoint_subnet_ids" {
   description = "The ID of one or more subnets in which to create a network interface for ECR api endpoint. If omitted, private subnets will be used."
+  type        = list(string)
   default     = []
 }
 
 variable "ecr_api_endpoint_private_dns_enabled" {
   description = "Whether or not to associate a private hosted zone with the specified VPC for ECR API endpoint"
+  type        = bool
   default     = false
 }
 
 variable "ecr_api_endpoint_security_group_ids" {
   description = "The ID of one or more security groups to associate with the network interface for ECR API endpoint"
+  type        = list(string)
   default     = []
 }
 
 variable "enable_ecr_dkr_endpoint" {
   description = "Should be true if you want to provision an ecr dkr endpoint to the VPC"
+  type        = bool
   default     = false
 }
 
 variable "ecr_dkr_endpoint_subnet_ids" {
   description = "The ID of one or more subnets in which to create a network interface for ECR dkr endpoint. If omitted, private subnets will be used."
+  type        = list(string)
   default     = []
 }
 
 variable "ecr_dkr_endpoint_private_dns_enabled" {
   description = "Whether or not to associate a private hosted zone with the specified VPC for ECR DKR endpoint"
+  type        = bool
   default     = false
 }
 
 variable "ecr_dkr_endpoint_security_group_ids" {
   description = "The ID of one or more security groups to associate with the network interface for ECR DKR endpoint"
+  type        = list(string)
   default     = []
 }
 
 variable "enable_kms_endpoint" {
   description = "Should be true if you want to provision a KMS endpoint to the VPC"
+  type        = bool
   default     = false
 }
 
 variable "kms_endpoint_security_group_ids" {
   description = "The ID of one or more security groups to associate with the network interface for KMS endpoint"
+  type        = list(string)
   default     = []
 }
 
 variable "kms_endpoint_subnet_ids" {
   description = "The ID of one or more subnets in which to create a network interface for KMS endpoint. Only a single subnet within an AZ is supported. If omitted, private subnets will be used."
+  type        = list(string)
   default     = []
 }
 
 variable "kms_endpoint_private_dns_enabled" {
   description = "Whether or not to associate a private hosted zone with the specified VPC for KMS endpoint"
+  type        = bool
   default     = false
 }
 
 variable "map_public_ip_on_launch" {
   description = "Should be false if you do not want to auto-assign public IP on launch"
+  type        = bool
   default     = true
 }
 
 variable "enable_vpn_gateway" {
   description = "Should be true if you want to create a new VPN Gateway resource and attach it to the VPC"
+  type        = bool
   default     = false
 }
 
@@ -366,268 +434,317 @@ variable "amazon_side_asn" {
 
 variable "propagate_private_route_tables_vgw" {
   description = "Should be true if you want route table propagation"
+  type        = bool
   default     = false
 }
 
 variable "propagate_public_route_tables_vgw" {
   description = "Should be true if you want route table propagation"
+  type        = bool
   default     = false
 }
 
 variable "tags" {
   description = "A map of tags to add to all resources"
+  type        = map(string)
   default     = {}
 }
 
 variable "vpc_tags" {
   description = "Additional tags for the VPC"
+  type        = map(string)
   default     = {}
 }
 
 variable "igw_tags" {
   description = "Additional tags for the internet gateway"
+  type        = map(string)
   default     = {}
 }
 
 variable "public_subnet_tags" {
   description = "Additional tags for the public subnets"
+  type        = map(string)
   default     = {}
 }
 
 variable "private_subnet_tags" {
   description = "Additional tags for the private subnets"
+  type        = map(string)
   default     = {}
 }
 
 variable "public_route_table_tags" {
   description = "Additional tags for the public route tables"
+  type        = map(string)
   default     = {}
 }
 
 variable "private_route_table_tags" {
   description = "Additional tags for the private route tables"
+  type        = map(string)
   default     = {}
 }
 
 variable "database_route_table_tags" {
   description = "Additional tags for the database route tables"
+  type        = map(string)
   default     = {}
 }
 
 variable "redshift_route_table_tags" {
   description = "Additional tags for the redshift route tables"
+  type        = map(string)
   default     = {}
 }
 
 variable "elasticache_route_table_tags" {
   description = "Additional tags for the elasticache route tables"
+  type        = map(string)
   default     = {}
 }
 
 variable "intra_route_table_tags" {
   description = "Additional tags for the intra route tables"
+  type        = map(string)
   default     = {}
 }
 
 variable "database_subnet_tags" {
   description = "Additional tags for the database subnets"
+  type        = map(string)
   default     = {}
 }
 
 variable "database_subnet_group_tags" {
   description = "Additional tags for the database subnet group"
+  type        = map(string)
   default     = {}
 }
 
 variable "redshift_subnet_tags" {
   description = "Additional tags for the redshift subnets"
+  type        = map(string)
   default     = {}
 }
 
 variable "redshift_subnet_group_tags" {
   description = "Additional tags for the redshift subnet group"
+  type        = map(string)
   default     = {}
 }
 
 variable "elasticache_subnet_tags" {
   description = "Additional tags for the elasticache subnets"
+  type        = map(string)
   default     = {}
 }
 
 variable "intra_subnet_tags" {
   description = "Additional tags for the intra subnets"
+  type        = map(string)
   default     = {}
 }
 
 variable "public_acl_tags" {
   description = "Additional tags for the public subnets network ACL"
+  type        = map(string)
   default     = {}
 }
 
 variable "private_acl_tags" {
   description = "Additional tags for the private subnets network ACL"
+  type        = map(string)
   default     = {}
 }
 
 variable "intra_acl_tags" {
   description = "Additional tags for the intra subnets network ACL"
+  type        = map(string)
   default     = {}
 }
 
 variable "database_acl_tags" {
   description = "Additional tags for the database subnets network ACL"
+  type        = map(string)
   default     = {}
 }
 
 variable "redshift_acl_tags" {
   description = "Additional tags for the redshift subnets network ACL"
+  type        = map(string)
   default     = {}
 }
 
 variable "elasticache_acl_tags" {
   description = "Additional tags for the elasticache subnets network ACL"
+  type        = map(string)
   default     = {}
 }
 
 variable "dhcp_options_tags" {
   description = "Additional tags for the DHCP option set (requires enable_dhcp_options set to true)"
+  type        = map(string)
   default     = {}
 }
 
 variable "nat_gateway_tags" {
   description = "Additional tags for the NAT gateways"
+  type        = map(string)
   default     = {}
 }
 
 variable "nat_eip_tags" {
   description = "Additional tags for the NAT EIP"
+  type        = map(string)
   default     = {}
 }
 
 variable "vpn_gateway_tags" {
   description = "Additional tags for the VPN gateway"
+  type        = map(string)
   default     = {}
 }
 
 variable "enable_dhcp_options" {
   description = "Should be true if you want to specify a DHCP options set with a custom domain name, DNS servers, NTP servers, netbios servers, and/or netbios server type"
+  type        = bool
   default     = false
 }
 
 variable "dhcp_options_domain_name" {
   description = "Specifies DNS name for DHCP options set (requires enable_dhcp_options set to true)"
+  type        = string
   default     = ""
 }
 
 variable "dhcp_options_domain_name_servers" {
   description = "Specify a list of DNS server addresses for DHCP options set, default to AWS provided (requires enable_dhcp_options set to true)"
-
-  default = ["AmazonProvidedDNS"]
+  type        = list(string)
+  default     = ["AmazonProvidedDNS"]
 }
 
 variable "dhcp_options_ntp_servers" {
   description = "Specify a list of NTP servers for DHCP options set (requires enable_dhcp_options set to true)"
-
-  default = []
+  type        = list(string)
+  default     = []
 }
 
 variable "dhcp_options_netbios_name_servers" {
   description = "Specify a list of netbios servers for DHCP options set (requires enable_dhcp_options set to true)"
-
-  default = []
+  type        = list(string)
+  default     = []
 }
 
 variable "dhcp_options_netbios_node_type" {
   description = "Specify netbios node_type for DHCP options set (requires enable_dhcp_options set to true)"
+  type        = string
   default     = ""
 }
 
 variable "manage_default_vpc" {
   description = "Should be true to adopt and manage Default VPC"
+  type        = bool
   default     = false
 }
 
 variable "default_vpc_name" {
   description = "Name to be used on the Default VPC"
+  type        = string
   default     = ""
 }
 
 variable "default_vpc_enable_dns_support" {
   description = "Should be true to enable DNS support in the Default VPC"
+  type        = bool
   default     = true
 }
 
 variable "default_vpc_enable_dns_hostnames" {
   description = "Should be true to enable DNS hostnames in the Default VPC"
+  type        = bool
   default     = false
 }
 
 variable "default_vpc_enable_classiclink" {
   description = "Should be true to enable ClassicLink in the Default VPC"
+  type        = bool
   default     = false
 }
 
 variable "default_vpc_tags" {
   description = "Additional tags for the Default VPC"
+  type        = map(string)
   default     = {}
 }
 
 variable "manage_default_network_acl" {
   description = "Should be true to adopt and manage Default Network ACL"
+  type        = bool
   default     = false
 }
 
 variable "default_network_acl_name" {
   description = "Name to be used on the Default Network ACL"
+  type        = string
   default     = ""
 }
 
 variable "default_network_acl_tags" {
   description = "Additional tags for the Default Network ACL"
+  type        = map(string)
   default     = {}
 }
 
 variable "public_dedicated_network_acl" {
   description = "Whether to use dedicated network ACL (not default) and custom rules for public subnets"
+  type        = bool
   default     = false
 }
 
 variable "private_dedicated_network_acl" {
   description = "Whether to use dedicated network ACL (not default) and custom rules for private subnets"
+  type        = bool
   default     = false
 }
 
 variable "intra_dedicated_network_acl" {
   description = "Whether to use dedicated network ACL (not default) and custom rules for intra subnets"
+  type        = bool
   default     = false
 }
 
 variable "database_dedicated_network_acl" {
   description = "Whether to use dedicated network ACL (not default) and custom rules for database subnets"
+  type        = bool
   default     = false
 }
 
 variable "redshift_dedicated_network_acl" {
   description = "Whether to use dedicated network ACL (not default) and custom rules for redshift subnets"
+  type        = bool
   default     = false
 }
 
 variable "elasticache_dedicated_network_acl" {
   description = "Whether to use dedicated network ACL (not default) and custom rules for elasticache subnets"
+  type        = bool
   default     = false
 }
 
 variable "default_network_acl_ingress" {
   description = "List of maps of ingress rules to set on the Default Network ACL"
+  type        = list(map(string))
 
-  default = [{
-    rule_no    = 100
-    action     = "allow"
-    from_port  = 0
-    to_port    = 0
-    protocol   = "-1"
-    cidr_block = "0.0.0.0/0"
-  },
+  default = [
+    {
+      rule_no    = 100
+      action     = "allow"
+      from_port  = 0
+      to_port    = 0
+      protocol   = "-1"
+      cidr_block = "0.0.0.0/0"
+    },
     {
       rule_no         = 101
       action          = "allow"
@@ -641,15 +758,17 @@ variable "default_network_acl_ingress" {
 
 variable "default_network_acl_egress" {
   description = "List of maps of egress rules to set on the Default Network ACL"
+  type        = list(map(string))
 
-  default = [{
-    rule_no    = 100
-    action     = "allow"
-    from_port  = 0
-    to_port    = 0
-    protocol   = "-1"
-    cidr_block = "0.0.0.0/0"
-  },
+  default = [
+    {
+      rule_no    = 100
+      action     = "allow"
+      from_port  = 0
+      to_port    = 0
+      protocol   = "-1"
+      cidr_block = "0.0.0.0/0"
+    },
     {
       rule_no         = 101
       action          = "allow"
@@ -663,6 +782,7 @@ variable "default_network_acl_egress" {
 
 variable "public_inbound_acl_rules" {
   description = "Public subnets inbound network ACLs"
+  type        = list(map(string))
 
   default = [
     {
@@ -678,6 +798,7 @@ variable "public_inbound_acl_rules" {
 
 variable "public_outbound_acl_rules" {
   description = "Public subnets outbound network ACLs"
+  type        = list(map(string))
 
   default = [
     {
@@ -693,6 +814,7 @@ variable "public_outbound_acl_rules" {
 
 variable "private_inbound_acl_rules" {
   description = "Private subnets inbound network ACLs"
+  type        = list(map(string))
 
   default = [
     {
@@ -708,6 +830,7 @@ variable "private_inbound_acl_rules" {
 
 variable "private_outbound_acl_rules" {
   description = "Private subnets outbound network ACLs"
+  type        = list(map(string))
 
   default = [
     {
@@ -723,6 +846,7 @@ variable "private_outbound_acl_rules" {
 
 variable "intra_inbound_acl_rules" {
   description = "Intra subnets inbound network ACLs"
+  type        = list(map(string))
 
   default = [
     {
@@ -738,6 +862,7 @@ variable "intra_inbound_acl_rules" {
 
 variable "intra_outbound_acl_rules" {
   description = "Intra subnets outbound network ACLs"
+  type        = list(map(string))
 
   default = [
     {
@@ -753,6 +878,7 @@ variable "intra_outbound_acl_rules" {
 
 variable "database_inbound_acl_rules" {
   description = "Database subnets inbound network ACL rules"
+  type        = list(map(string))
 
   default = [
     {
@@ -768,6 +894,7 @@ variable "database_inbound_acl_rules" {
 
 variable "database_outbound_acl_rules" {
   description = "Database subnets outbound network ACL rules"
+  type        = list(map(string))
 
   default = [
     {
@@ -783,6 +910,7 @@ variable "database_outbound_acl_rules" {
 
 variable "redshift_inbound_acl_rules" {
   description = "Redshift subnets inbound network ACL rules"
+  type        = list(map(string))
 
   default = [
     {
@@ -798,6 +926,7 @@ variable "redshift_inbound_acl_rules" {
 
 variable "redshift_outbound_acl_rules" {
   description = "Redshift subnets outbound network ACL rules"
+  type        = list(map(string))
 
   default = [
     {
@@ -813,6 +942,7 @@ variable "redshift_outbound_acl_rules" {
 
 variable "elasticache_inbound_acl_rules" {
   description = "Elasticache subnets inbound network ACL rules"
+  type        = list(map(string))
 
   default = [
     {
@@ -828,6 +958,7 @@ variable "elasticache_inbound_acl_rules" {
 
 variable "elasticache_outbound_acl_rules" {
   description = "Elasticache subnets outbound network ACL rules"
+  type        = list(map(string))
 
   default = [
     {
@@ -840,3 +971,4 @@ variable "elasticache_outbound_acl_rules" {
     },
   ]
 }
+