This directive is equivalent to Redirect, but makes use of standard
regular expressions, instead of simple prefix matching. The
supplied regular expression is matched against the URL-path,
and if it matches, the server will substitute any parenthesized
matches into the given string and use it as a filename. For
example, to redirect all GIF files to like-named JPEG files on
another server, one might use:
RedirectMatch (.*).gif$ http://www.anotherserver.com$1.jpg