yes it is being pulled from an http server (apache), but how would I get 
  the XML representation of the filesystem? Is that something I can create 
  with an xslt stylesheet?

cocoon has a directory lister built in if I remember correctly, 
er yes:
http://cocoon.apache.org/2.1/userdocs/generators/directory-generator.html

or you can do something simpler like just setting up a redirect from
foo/bar
to
cgi-bin/directory-list?dir=foo/bar
where directory-list is essentially the perl script that you have
already that returns an xml listing of the directory files.

http://www.google.co.uk/search?hl=en&q=apache+xslt+directory+list&spell=1

has some possibilities...

David

________________________________________________________________________
This e-mail has been scanned for all viruses by Star. The
service is powered by MessageLabs. For more information on a proactive
anti-virus service working around the clock, around the globe, visit:
http://www.star.net.uk
________________________________________________________________________