Apache Reference: mod_alias, AliasMatch
Map a URL to a File Name Path via Regular Expression Match
Syntax: AliasMatch url-pattern A
Example: AliasMatch ^(.+\.(gif))$ /www/$2/$1
Since: Apache 1.3
This directive is equivalent to Alias, but uses standard
regular expressions, instead of simple prefix matching. The
supplied regular expression url-pattern is compared with
the request URL. If it matches, the server will substitute any
matches found in parentheses in fs-path into the given
string and use it as a file system path. For instance, in the
preceding example, a request for http://host/foo/bar.gif
would cause the server to return the file F.