mod_accel ( http://sysoev.ru/en/ ) allows to take cookies into account while caching:
AccelCacheCookie some_cookie_name another_cookie_name
You can set it on per-location basis.
Besides, my upcoming light-weight http and reverse proxy server nginx will allow to do it too.
Double check first whether this is allowed by RFC2616 - remember that the Apache mod_proxy is very unlikely to be the only proxy in the chain, so even if mod_proxy takes cookies into account, other caches in the chain might not.
Also, it is unlikely that changes will be made to the v1.3 tree code, it is more likely that such a feature might be found in the mod_cache modules of Apache v2.0.
The original design of mod_cache allowed for the caching of different variants of the same URL (different variants might be different languages of the same page, etc), though I am not sure if that feature currently works. If it does, that would be what you need.
Regards, Graham --
