diff --git a/README.md b/README.md
index b1762f5..e03856e 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,7 @@ Create a workflow `.yml` file in your repositories `.github/workflows` directory
 ### Inputs
 
 * `packages` - Space delimited list of packages to install.
+* `version` - Version of cache to load. Each version will have its own cache. Note, all characters except spaces are allowed.
 
 ### Outputs
 
@@ -44,6 +45,7 @@ jobs:
       - uses: awalsh128/cache-apt-pkgs-action@v1
         with:
           packages: dia doxygen doxygen-doc doxygen-gui doxygen-latex graphviz mscgen
+          version: 1.0
 
       - name: Build        
         run: |
diff --git a/action.yml b/action.yml
index 1675e0c..67ebb1c 100644
--- a/action.yml
+++ b/action.yml
@@ -10,36 +10,42 @@ inputs:
     description: 'Space delimited list of packages to install.'
     required: true
     default: ''
+  version:
+    description: 'Version will create a new cache and install packages.'
+    required: false
+    default: ''
 
 outputs:
   cache-hit:
     description: 'A boolean value to indicate a cache was found for the packages requested.'
-    value: ${{ steps.load-pkg-cache.outputs.cache-hit }}
+    # This compound expression is needed because lhs can be empty.
+    # Need to output true and false instead of true and nothing.
+    value: ${{ steps.load-cache.outputs.cache-hit || false }}
 
 runs:
   using: "composite"
   steps:
     - name: Validate Packages
-      run: ${{ github.action_path }}/validate_pkgs.sh ${{ inputs.packages }}
+      run: ${{ github.action_path }}/validate_pkgs.sh "${{ inputs.version }}" ${{ inputs.packages }}
       shell: bash
 
     - name: Create Cache Key
-      run: echo ${{ inputs.packages }} | sed 's/[\s,]+/\n/g' | sort > /tmp/package_list.txt
+      run: |
+        ${{ github.action_path }}/create_cache_key.sh "${{ inputs.version }})" ${{ inputs.packages }}
       shell: bash
 
     - name: Load Package Cache
-      id: load-pkg-cache
+      id: load-cache
       uses: actions/cache@v2
       with:
         path: ~/cache-apt-pkgs
-        key: cache-apt-pkgs_${{ hashFiles('/tmp/package_list.txt') }}
+        key: cache-apt-pkgs_${{ env.CACHE_KEY }}
 
-    - name: Install and Cache Packages
-      if: steps.load-pkg-cache.outputs.cache-hit != 'true'
-      run: ${{ github.action_path }}/install_and_cache.sh ~/cache-apt-pkgs ${{ inputs.packages }}
-      shell: bash
-
-    - name: Restore Cached Packages
-      if: steps.load-pkg-cache.outputs.cache-hit != 'true'
-      run: ${{ github.action_path }}/run.sh ~/cache-apt-pkgs /
+    - name: Load Packages      
+      run: |
+        if [ ${{ steps.load-cache.outputs.cache-hit }} ]; then
+          ${{ github.action_path }}/restore_pkgs.sh ~/cache-apt-pkgs /
+        else
+          ${{ github.action_path }}/install_and_cache_pkgs.sh ~/cache-apt-pkgs ${{ inputs.packages }}
+        fi
       shell: bash
diff --git a/create_cache_key.sh b/create_cache_key.sh
new file mode 100755
index 0000000..9d5c98f
--- /dev/null
+++ b/create_cache_key.sh
@@ -0,0 +1,21 @@
+#!/bin/bash
+
+# Fail on any error.
+set -e
+
+version=$1
+packages=${@:2}
+
+echo "* Creating cache key..."
+
+# Remove package delimiters, sort (requires newline) and then convert back to inline list.
+normalized_list=$(echo $packages | sed 's/[\s,]+/ /g' | tr ' ' '\n' | sort | tr '\n' ' ')
+echo "* Normalized package list is '$normalized_list'."
+
+value=$(echo $normalized_list @ $version)
+echo "* Value to hash is '$value'."
+
+key=$(echo $value | md5sum | /bin/cut -f1 -d' ')
+echo "* Value hashed as '$key'."
+
+echo "CACHE_KEY=$key" >> $GITHUB_ENV
\ No newline at end of file
diff --git a/install_and_cache_pkgs.sh b/install_and_cache_pkgs.sh
index e73b978..9d68cf8 100755
--- a/install_and_cache_pkgs.sh
+++ b/install_and_cache_pkgs.sh
@@ -1,10 +1,19 @@
 #!/bin/bash
 
+# Fail on any error.
+set -e
+
 # Directory that holds the cached packages.
 cache_dir=$1
 # List of the packages to use.
 packages="${@:2}"
 
+package_count=$(echo $packages | wc -w)
+echo "* Clean installing $package_count packages..."
+for package in $packages; do
+  echo "  - $package"
+done
+
 mkdir -p $cache_dir
 for package in $packages; do
   cache_filepath=$cache_dir/$package.tar.gz
@@ -19,6 +28,6 @@ for package in $packages; do
       if test -f $f; then echo $f; fi;
     done | 
     xargs tar -czf $cache_filepath -C /
-fi
+done
 
-echo "Action complete. ${#packages[@]} package(s) installed and cached."
+echo "Action complete. $(echo $packages | wc -w) package(s) installed and cached."
diff --git a/restore_pkgs.sh b/restore_pkgs.sh
index c83c6ea..9f151e6 100755
--- a/restore_pkgs.sh
+++ b/restore_pkgs.sh
@@ -1,15 +1,30 @@
 #!/bin/bash
 
+# Fail on any error.
+set -e
+
 # Directory that holds the cached packages.
 cache_dir=$1
 # Root directory to untar the cached packages to.
 # Typically filesystem root '/' but can be changed for testing.
 cache_restore_root=$2
+# List of the packages to use.
+packages="${@:3}"
 
-for cache_filepath in $(ls $cache_dir); do
-  echo "* Restoring $package from cache $cache_filepath... "
+cache_filenames=$(ls -1 $cache_dir | sort)
+cache_filename_count=$(echo $cache_filenames | wc -w)
+echo "* Found $cache_filename_count files in cache..."
+for cache_filename in $cache_filenames; do
+  echo "  - $cache_filename"
+done
+
+for package in $packages; do
+  cache_filepath=$cache_dir/$package.tar.gz
+  echo "* Restoring package $package ($cache_filepath) from cache... "
   sudo tar -xf $cache_filepath -C $cache_restore_root
+  # Upgrade the install from last state.
+  # TODO(awalsh128) Add versioning to cache key creation.
   sudo apt-get --yes --only-upgrade install $package
-fi
+done
 
-echo "Action complete. ${#packages[@]} package(s) restored."
+echo "Action complete. $cache_filename_count package(s) restored."
diff --git a/validate_pkgs.sh b/validate_pkgs.sh
index 09e3e52..e06e463 100755
--- a/validate_pkgs.sh
+++ b/validate_pkgs.sh
@@ -1,19 +1,30 @@
 #!/bin/bash
 
-packages=$1
+version=$1
+packages=${@:2}
 
 echo -n "* Validating action arguments... ";
+
+echo $version | grep -o " " > /dev/null
+if [ $? -eq 0 ]; then
+  echo "aborted."
+  echo "* Version value '$version' cannot contain spaces." >&2
+  exit 1
+fi
+
 if [ "$packages" == "" ]; then
   echo "aborted."
   echo "* Packages argument cannot be empty." >&2
-  exit 1
+  exit 2
 fi
+
 for package in $packages; do
   apt-cache search ^$package$ | grep $package > /dev/null
   if [ $? -ne 0 ]; then
     echo "aborted."
     echo "* Package '$package' not found." >&2
-    exit 2
+    exit 3
   fi
 done
+
 echo "done."