I'm trying to mirror a site that has an "exit page" - basically a page that
says "you are now leaving XYZ, click here to continue".

The page is called with the target URL in the QueryString:

exit.php?www.google.com

While the page is a PHP page, the redirection is actually handled with
client-side javascript, so exactly the same page is returned no matter what
query-string is appended. 

Right now, exit.php?www.google.com becomes 
exit1234.html?www.google.com and exit.php?www.bing.com becomes
exit3456.html?www.bing.com

Is there a way to disable the creation of individual copies of exit.html,
while keeping the queries-strings in the calling links?