Varnish 4 purge

Hello,
VCL provided for Varnish 4 includes commented lines about purge. I tried to use the code included for purge method, but it does not work.

My varnishadm does not work as expected and Drupal Varnish module cannot exec ban command. I try to figure how to use Drupal Purge module to avoid Varnish Administration

I tried return purge as usual, and later i tried return hash (as provided at example).

My default.vcl has:

acl purge {
  "localhost";
  "127.0.0.1";
}

// TODO: Add purge handler, access checks and other stuff relying on
  // non-standard HTTP verbs here.

  // /**
  //  * Example 1: Allow purge from all clients in the purge-acl. Note that
  //  * additional VCL is necessary to make this work, notably the acl and some
  //  * code in vcl_backend_fetch and vcl_hit.
  //  *
  //  * More information on:
  //  * https://www.varnish-cache.org/docs/3.0/tutorial/purging.html
  //  */
  // if (req.method == "PURGE") {
  //   if (!client.ip ~ purge) {
  //     return (synth(405));
  //   }
  //   return (hash);
  // }
  # Check the incoming request type is "PURGE", not "GET" or "POST".
  if (req.method == "PURGE") {
    # Check if the IP is allowed.
    if (!client.ip ~ purge) {
      # Return error code 405 (Forbidden) when not.
      return (synth(405, "Not allowed:"));
    }
    return (hash);
// This return is the standard return, but it is not used at provided example
# return (purge);
  }

I did not found any other comment about purge, also i was googling for some days, but all the standar methods does not work for me.
I think the clue would be this part of comment:
and some code in vcl_backend_fetch and vcl_hit.

Have anybody experience with purge method and Authcache vcl?
Can you give me any suggestion about the code should i write in vcl_backend_fetch or vcl_hit?

Also i added a condition to allow me see fresh content with CTRL + F5:

if (req.http.cache-control == "no-cache")
{
#       return (pass);
return (hash);
}

I changed return pass for return hash to follow the tip above, and i can get a fresh page content the first load, but sucesive reloads with F5 continues returning the old cached content.

I think i can became rewriting vcl and continue investigating if anybody can suggest me how to force Varnish to rebuild the cache for a URL, based on Authcache vcl.

Any suggestion will be appreciated.

Thanks.
Jose