diff --git a/.copier-answers.yml b/.copier-answers.yml
index 036fc73..89b3210 100644
--- a/.copier-answers.yml
+++ b/.copier-answers.yml
@@ -1,5 +1,5 @@
 # Changes here will be overwritten by Copier
-_commit: v1.7.8
+_commit: v1.7.9
 _src_path: https://github.com/DeveloperC286/template
 project_name: monkey_interpreter
 project_type: rust
diff --git a/.github/workflows/continuous-delivery.yml b/.github/workflows/continuous-delivery.yml
index 94af38c..3707b18 100644
--- a/.github/workflows/continuous-delivery.yml
+++ b/.github/workflows/continuous-delivery.yml
@@ -18,14 +18,30 @@ jobs:
         architecture: [ubuntu-24.04, ubuntu-24.04-arm]
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       - name: Setup Nix.
-        uses: cachix/install-nix-action@ab739621df7a23f52766f9ccc97f38da6b7af14f # v31.10.5
+        uses: cachix/install-nix-action@8aa03977d8d733052d78f4e008a241fd1dbf36b3 # v31.10.6
       - name: Publish binary.
         run: nix develop -c make publish-binary RELEASE="${GITHUB_REF_NAME}"
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }} # This token is provided by GitHub Actions.
 
+<<<<<<< before updating
+=======
+  publish-crate:
+    name: Publish Crate
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout code.
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+      - name: Setup Nix.
+        uses: cachix/install-nix-action@8aa03977d8d733052d78f4e008a241fd1dbf36b3 # v31.10.6
+      - name: Publish crate.
+        run: nix develop -c make publish-crate
+        env:
+          CARGO_REGISTRY_TOKEN: ${{ secrets.CARGO_REGISTRY_TOKEN }}
+
+>>>>>>> after updating
   publish-docker-image:
     name: Publish Docker Image (${{ matrix.platform }})
     runs-on: ${{ matrix.runner }}
@@ -43,11 +59,11 @@ jobs:
             suffix: arm64
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@4d04d5d9486b7bd6fa91e7baf45bbb4f8b9deedd # v4.0.0
+        uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
       - name: Login to GitHub Container Registry
-        uses: docker/login-action@4907a6ddec9925e35a0a9e82d7399ccc52663121 # v4.1.0
+        uses: docker/login-action@af1e73f918a031802d376d3c8bbc3fe56130a9b0 # v4.4.0
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
@@ -63,11 +79,11 @@ jobs:
     needs: [publish-docker-image]
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@4d04d5d9486b7bd6fa91e7baf45bbb4f8b9deedd # v4.0.0
+        uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
       - name: Login to GitHub Container Registry
-        uses: docker/login-action@4907a6ddec9925e35a0a9e82d7399ccc52663121 # v4.1.0
+        uses: docker/login-action@af1e73f918a031802d376d3c8bbc3fe56130a9b0 # v4.4.0
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index 38e05e5..75d8ef5 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -15,7 +15,7 @@ jobs:
         language: [shell]
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       - name: Check permissions.
         run: make check-${{ matrix.language }}-permissions
 
@@ -28,9 +28,9 @@ jobs:
         language: [rust, shell]
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       - name: Setup Nix.
-        uses: cachix/install-nix-action@ab739621df7a23f52766f9ccc97f38da6b7af14f # v31.10.5
+        uses: cachix/install-nix-action@8aa03977d8d733052d78f4e008a241fd1dbf36b3 # v31.10.6
       - name: Check formatting.
         run: nix develop -c make check-${{ matrix.language }}-formatting
 
@@ -43,9 +43,9 @@ jobs:
         language: [rust, shell]
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       - name: Setup Nix.
-        uses: cachix/install-nix-action@ab739621df7a23f52766f9ccc97f38da6b7af14f # v31.10.5
+        uses: cachix/install-nix-action@8aa03977d8d733052d78f4e008a241fd1dbf36b3 # v31.10.6
       - name: Check linting.
         run: nix develop -c make check-${{ matrix.language }}-linting
 
@@ -58,9 +58,9 @@ jobs:
         language: [rust]
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       - name: Setup Nix.
-        uses: cachix/install-nix-action@ab739621df7a23f52766f9ccc97f38da6b7af14f # v31.10.5
+        uses: cachix/install-nix-action@8aa03977d8d733052d78f4e008a241fd1dbf36b3 # v31.10.6
       - name: Check dependencies.
         run: nix develop -c make check-${{ matrix.language }}-dependencies
 
@@ -72,9 +72,9 @@ jobs:
         architecture: [ubuntu-24.04, ubuntu-24.04-arm]
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       - name: Setup Nix.
-        uses: cachix/install-nix-action@ab739621df7a23f52766f9ccc97f38da6b7af14f # v31.10.5
+        uses: cachix/install-nix-action@8aa03977d8d733052d78f4e008a241fd1dbf36b3 # v31.10.6
       - name: Compile.
         run: nix develop -c make compile
 
@@ -86,8 +86,25 @@ jobs:
         architecture: [ubuntu-24.04, ubuntu-24.04-arm]
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       - name: Setup Nix.
-        uses: cachix/install-nix-action@ab739621df7a23f52766f9ccc97f38da6b7af14f # v31.10.5
+        uses: cachix/install-nix-action@8aa03977d8d733052d78f4e008a241fd1dbf36b3 # v31.10.6
       - name: Unit test.
         run: nix develop -c make unit-test
+<<<<<<< before updating
+=======
+
+  end-to-end-test:
+    name: End to End Test
+    runs-on: ${{ matrix.architecture }}
+    strategy:
+      matrix:
+        architecture: [ubuntu-24.04, ubuntu-24.04-arm]
+    steps:
+      - name: Checkout code.
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+      - name: Setup Nix.
+        uses: cachix/install-nix-action@8aa03977d8d733052d78f4e008a241fd1dbf36b3 # v31.10.6
+      - name: End to End test.
+        run: nix develop -c make end-to-end-test
+>>>>>>> after updating
diff --git a/.github/workflows/conventional-commits.yml b/.github/workflows/conventional-commits.yml
index 4906890..84d48a6 100644
--- a/.github/workflows/conventional-commits.yml
+++ b/.github/workflows/conventional-commits.yml
@@ -15,7 +15,7 @@ jobs:
       image: ghcr.io/developerc286/conventional_commits_linter:0.17.1@sha256:f1b947937ee884ba7f886d04939cd4858f9aeafb50dcf94925a516c50e43021b
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           ref: ${{ github.event.pull_request.head.sha }}
           fetch-depth: 0
diff --git a/.github/workflows/git-history.yml b/.github/workflows/git-history.yml
index 8aaedad..d00ddf7 100644
--- a/.github/workflows/git-history.yml
+++ b/.github/workflows/git-history.yml
@@ -13,7 +13,7 @@ jobs:
       image: ghcr.io/developerc286/clean_git_history:1.2.0@sha256:bdbd6ca09529f44010583fd89528a96961f7acb12bdd7baa975b0811032a647e
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           ref: ${{ github.event.pull_request.head.sha }}
           fetch-depth: 0
diff --git a/.github/workflows/github-actions-workflows.yml b/.github/workflows/github-actions-workflows.yml
index 75a8c16..72399b9 100644
--- a/.github/workflows/github-actions-workflows.yml
+++ b/.github/workflows/github-actions-workflows.yml
@@ -14,9 +14,9 @@ jobs:
         architecture: [ubuntu-24.04, ubuntu-24.04-arm]
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       - name: Setup Nix.
-        uses: cachix/install-nix-action@ab739621df7a23f52766f9ccc97f38da6b7af14f # v31.10.5
+        uses: cachix/install-nix-action@8aa03977d8d733052d78f4e008a241fd1dbf36b3 # v31.10.6
       - name: Check formatting.
         run: nix develop -c make check-yaml-formatting
 
@@ -28,8 +28,8 @@ jobs:
         architecture: [ubuntu-24.04, ubuntu-24.04-arm]
     steps:
       - name: Checkout code.
-        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       - name: Setup Nix.
-        uses: cachix/install-nix-action@ab739621df7a23f52766f9ccc97f38da6b7af14f # v31.10.5
+        uses: cachix/install-nix-action@8aa03977d8d733052d78f4e008a241fd1dbf36b3 # v31.10.6
       - name: Check GitHub Actions workflows linting.
         run: nix develop -c make check-github-actions-workflows-linting
diff --git a/.gitignore b/.gitignore
index 2b4217c..64e259f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,5 +9,8 @@ target
 # Generated by proptest
 proptest-regressions
 
-# Generated by direnv & Nix.
+# Generated by direnv.
 .direnv
+
+# Generated by Nix.
+result