diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6ad464d..ba1f121 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -3,14 +3,16 @@ name: CI
 on:
   pull_request:
   push:
-    branches: [ main ]
+    branches:
+      - 'main'
+      - 'v[0-9]+'
 
 jobs:
   build:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3
-    - run: npm ci --ignore-scripts
+    - run: npm install --ignore-scripts
     - run: echo "$PWD/node_modules/.bin" >> "$GITHUB_PATH"
     - run: deno test --no-run
     - run: deno lint
@@ -19,5 +21,5 @@ jobs:
     - run: lib/cli.js --outDir nodejs/
     - run: git diff --no-index lib/ nodejs/
 
-    - run: deno test --allow-read=.
+    - run: deno test --allow-read=. src/
     - run: fdt lib/**/*.test.js
diff --git a/src/_transformations/specifiers.ts b/src/_transformations/specifiers.ts
index 1bf693b..bea9ab2 100644
--- a/src/_transformations/specifiers.ts
+++ b/src/_transformations/specifiers.ts
@@ -1,26 +1,14 @@
+import { Node, type SourceFile } from "../deps.deno.ts";
 import * as re from "../util/regexp.ts";
 
-export const name = /(?:@[\w.-]+\/)?[\w.-]+/;
-const version = /[^/?]+/;
+export const services = ["npm:", "https://esm.sh/", "https://cdn.skypack.dev/"];
+export const name = /^(?:@[\w.-]+\/)?[\w.-]+$/;
+const version = /^@[^/?]+$/;
 const path = /\/[^?]*/;
+const url = re.tag()`^${re.union(services)}(${name})${version}?(${path})?.*$`;
 
-const patterns = [
-  re.tag()`^npm:(${name})(?:@${version})?(${path})?`,
-  re.tag()`^https://esm\.sh/(${name})(?:@${version})?(${path})?`,
-  re.tag()`^https://cdn\.skypack\.dev/(${name})(?:@${version})?(${path})?`,
-  re.tag()`^https://deno\.land/std(?:@${version})?/node/([\w/]+)\.ts$`,
-  re.tag()`^https://nest\.land/std/node/${version}/([\w/]+)\.ts$`,
-];
-
-const transpileHttpsImport = (specifier: string) => {
-  for (const pattern of patterns) {
-    const match = pattern.exec(specifier);
-    if (match === null) continue;
-    const [, pkg, path = ""] = match;
-    return pkg + path;
-  }
-  return specifier;
-};
+const transpileHttpsImport = (specifier: string) =>
+  specifier.replace(url, "$1$2");
 
 const transpileRelativeImport = (specifier: string) =>
   specifier
@@ -33,3 +21,17 @@ export const transpileSpecifier = (specifier: string) => {
   if (isRelative(specifier)) return transpileRelativeImport(specifier);
   return transpileHttpsImport(specifier);
 };
+
+export function transpileSpecifiers(sourceFile: SourceFile) {
+  for (const statement of sourceFile.getStatements()) {
+    if (
+      Node.isImportDeclaration(statement) ||
+      Node.isExportDeclaration(statement)
+    ) {
+      const modSpecifierValue = statement.getModuleSpecifierValue();
+      if (modSpecifierValue !== undefined) {
+        statement.setModuleSpecifier(transpileSpecifier(modSpecifierValue));
+      }
+    }
+  }
+}
diff --git a/src/util/regexp.ts b/src/util/regexp.ts
index 068694a..36667b9 100644
--- a/src/util/regexp.ts
+++ b/src/util/regexp.ts
@@ -3,7 +3,7 @@ export type RegExpSource = Pick<RegExp, "source">;
 const _source = (arg: string | RegExpSource) =>
   typeof arg === "string"
     ? arg.replace(/[.*+?^${}()|[\]\\]/g, "\\$&") // escape string
-    : arg.source;
+    : arg.source.replace(/^\^|\$$/g, "");
 
 export const tag = (flags = "") =>
 (