hoonz, you can't just print a URL and hope for a redirect, you have to print a properly formatted redirect header.
What your script prints is just the url, "http://www.mysite.com/cgi-bin/forum.pl". That isn't enought to cause a browser to redirect, it has to look something like "Location: http://www.mysite.com/cgi-bin/forum.pl\n\n". Headers like these are easy to screw up- browsers care or don't care about capitalization and newlines with no rhyme or reason.
Projekt21 showed you the "correct" way to do this, and his/her version has nothing to do with mod_perl. Using CGI to print headers will save you much time debugging, and will create what you can be sure of are good headers.
-Any sufficiently advanced technology is
indistinguishable from doubletalk.