This isn't anywhere near as slick as fletch's solution.. however, I know you're a mod_perl guy.. so if you have your application running under mod_perl, you could always make use of mod_perl's status page, which lists all the loaded modules.

Althought I know you know this, for the benefit of everyone else, you can put this code into your httpd.conf to give yourself access to a mod_perl status report:

 
 <Location /perl-status>
   SetHandler  perl-script
   PerlHandler Apache::Status
 </Location>
[download]

Then you just fire up your browser, and wander over to http://www.mydomain.com/perl-status.

So if project X that you're working on now is the only Perl app loaded under mod_perl, it'd be pretty simple to figure out which modules it's using.

TMTOWTDI ;-)

-Eric