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 dfa60e5..f53bcd4 100644
--- a/action.yml
+++ b/action.yml
@@ -26,14 +26,12 @@ 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: |
-        normalized_list=$(echo ${{ inputs.packages }} | sed 's/[\s,]+/ /g' | sort)
-        value=$(echo $normalized_list @ ${{ inputs.version }})
-        echo "CACHE_KEY=$(echo $value | md5sum | /bin/cut -f1 -d' ')" >> $GITHUB_ENV
+        ${{ github.action_path }}/create_cache_key.sh "${{ inputs.version }})"" ${{ inputs.packages }} >> $GITHUB_ENV
       shell: bash
 
     - name: Load Package Cache
diff --git a/create_cache_key.sh b/create_cache_key.sh
new file mode 100755
index 0000000..679c672
--- /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"
\ No newline at end of file
diff --git a/validate_pkgs.sh b/validate_pkgs.sh
index 3b63a70..34c9830 100755
--- a/validate_pkgs.sh
+++ b/validate_pkgs.sh
@@ -3,20 +3,31 @@
 # Fail on any error.
 set -e
 
-packages=$1
+version=$1
+packages=${@:2}
 
 echo -n "* Validating action arguments... ";
+
+echo $version | grep -o " " > /dev/null
+if [ $? -ne 0 ]; then
+    echo "aborted."
+    echo "* Version value '$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."