[squid-users] how to write this urlpath_regex

hello,list.
      I get a problem when I write a filter rule. I have two urls.
http://host/bbs/1.php and http://host/bbs/foo/bar/x.jpg
      now,I want the squid can cache the jpg file but no cache for php
or other script file.
if I use urlpath_regex bbs php or other rule,the
http://host/bbs/foo/bar/x.jpg wile be filter too.
so ,how to write a rule,fileter bbs in the url but if have jpg ,then not filter.

-- 
Huang Mingyou