diff --git a/mrblib/rf/container.rb b/mrblib/rf/container.rb
index 14ef003..0a60b7e 100644
--- a/mrblib/rf/container.rb
+++ b/mrblib/rf/container.rb
@@ -38,6 +38,10 @@ def hash?
       _.instance_of?(Hash)
     end
 
+    def array?
+      _.instance_of?(Array)
+    end
+
     def puts(*)
       $output.write(generate_line_prefix)
       $output.puts(*)
@@ -62,6 +66,18 @@ def generate_line_prefix
       end
     end
 
+    %i[dig].each do |sym|
+      define_method(sym) do |*args|
+        _.__send__(sym, *args) if hash?
+      end
+    end
+
+    %i[grep grep_v].each do |sym|
+      define_method(sym) do |*args, &block|
+        _.__send__(sym, *args, &block) if array?
+      end
+    end
+
     def match(condition)
       regexp = if condition.is_a?(Regexp)
                  condition
@@ -83,12 +99,6 @@ def match?(condition)
     end
     alias m? match?
 
-    %i[dig].each do |sym|
-      define_method(sym) do |*args|
-        _.__send__(sym, *args) if hash?
-      end
-    end
-
     def respond_to_missing?(sym, *)
       # check for _0, _1, _2, _3, ...
       sym.to_s =~ /\A_(0|[1-9]\d*)\z/ || super
diff --git a/spec/container/instance_methods_spec.rb b/spec/container/instance_methods_spec.rb
index e6550a9..f1bfcac 100644
--- a/spec/container/instance_methods_spec.rb
+++ b/spec/container/instance_methods_spec.rb
@@ -27,6 +27,20 @@
     it_behaves_like 'a successful exec'
   end
 
+  where(:command, :expect_output) do
+    'grep(/foo/)'   | %w[foo].join("\n")
+    'grep_v(/bar/)' | %w[foo baz].join("\n")
+    'grep(/foo/){|i| i + "hoge" }' | %w[foohoge].join("\n")
+    'grep_v(/bar/){|i| i+ "hoge" }' | %w[foohoge bazhoge].join("\n")
+  end
+
+  with_them do
+    let(:input) { %w[foo bar baz].join("\n") }
+    let(:args) { %(-s '#{command}') }
+
+    it_behaves_like 'a successful exec'
+  end
+
   %w[match m].each do |method|
     describe "Container##{method}" do
       where do
@@ -214,67 +228,3 @@
     end
   end
 end
-
-# describe 'Method' do
-#
-#
-#  describe '#sub' do
-#    let(:input) { 'foofoo' }
-#    let(:output) do
-#      <<~OUTPUT
-#        barfoo
-#        foofoo
-#      OUTPUT
-#    end
-#
-#    before { run_rf(%q('puts sub(/foo/, "bar"); _'), input) }
-#
-#    it { expect(last_command_started).to be_successfully_executed }
-#    it { expect(last_command_started).to have_output output_string_eq output }
-#  end
-#
-#  describe '#sub!' do
-#    let(:input) { 'foofoo' }
-#    let(:output) do
-#      <<~OUTPUT
-#        barfoo
-#        barfoo
-#      OUTPUT
-#    end
-#
-#    before { run_rf(%q('puts sub!(/foo/, "bar"); _'), input) }
-#
-#    it { expect(last_command_started).to be_successfully_executed }
-#    it { expect(last_command_started).to have_output output_string_eq output }
-#  end
-#
-#  describe '#tr' do
-#    let(:input) { 'foo' }
-#    let(:output) do
-#      <<~OUTPUT
-#        FOO
-#        foo
-#      OUTPUT
-#    end
-#
-#    before { run_rf(%q('puts tr("a-z", "A-Z"); _'), input) }
-#
-#    it { expect(last_command_started).to be_successfully_executed }
-#    it { expect(last_command_started).to have_output output_string_eq output }
-#  end
-#
-#  describe '#tr!' do
-#    let(:input) { 'foo' }
-#    let(:output) do
-#      <<~OUTPUT
-#        FOO
-#        FOO
-#      OUTPUT
-#    end
-#
-#    before { run_rf(%q('puts tr!("a-z", "A-Z"); _'), input) }
-#
-#    it { expect(last_command_started).to be_successfully_executed }
-#    it { expect(last_command_started).to have_output output_string_eq output }
-#  end
-# end