title: Apache ProxyPass with dynamic hostname
body: <p>I'm trying to use Apache as a gateway to reverse proxy to a backend server with the same name as the requested http_host.</p>
  
  <p>ex:</p>
  
  <pre><code>    ProxyPass            /  https://%{HTTP_HOST}/
      ProxyPassReverse     /  https://%{HTTP_HOST}/
  </code></pre>
  
  <p>I'm getting an error when I use this setup.  Suggestions?</p>