Hi.
After upgrading my box to a newer Debian, I obtain this error when using your plugin. It seems that the explanation is that a function has been removed in PHP 5.4 (in my old box I was using PHP 5.3, now I use PHP 5.4):
http://php.net/manual/en/language.references.pass.php
Are you thinking about giving support to 5.4 version or should I start looking for anything else?
Thanks and best regards
http://wordpress.org/extend/plugins/wordpress-varnish-as-a-service/