Proxy cache only is cookie present

[nfn]

Hello,

I'm using nginx/0.7.62 to proxy requests to apache2+mod_php and I would like to cache content only if a cookie has a value present: "usergroup = 1"

How am I able to archive this?

Thanks

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,26770,26770#msg-26770