The purge tool is a kind of magnifying glass into your squid-2 cache.
You can use purge to have a look at what URLs are stored in which file
within your cache.  The purge tool can also be used to release objects
which URLs match user specified regular expressions.  It can extract
objects matching a regular expression, creating a directory tree
matching the server layout.  A more troublesome feature is the ability
to remove files squid does not seem to know about any longer.