title: How to change the purge url on save
body: <p>I have a plone website on which I want to set up a Varnish cache. The caching part is working great, but I have problems on the purging part. </p>
  
  <p>On my setup, the "view" URL and the "edit" URL are on two different names (eg. <code>myexample.com</code> and <code>plone.example.com/MyExample/</code>) and this Plone is on a multisite environment. </p>
  
  <p>Up to this point, when I save a page on the "edit server", it sends a purge request, but on the "edit" URL. (eg. on <code>/MyExample/my/path</code> instead of <code>/my/path</code>). </p>
  
  <p>Question is : what's the easiest / best way to rewrite the purge URL to remove the leading <code>/MyExample</code> part ?</p>
  
  <p>I am new to Plone and to Varnish, so any help is appreciated. </p>