One other comment in addition to DamnDirtyApe's excellent post - you should set the POST_MAX to a reasonable number. Otherwise someone could upload a 20GB file filling your drive, effectively creating a DOS attack.

$CGI::POST_MAX = 1024 * 1000 # 1MB

You mentioned you are new to programming Perl, so for dealing with CGI applications I would highly recommend using Ovid's CGI::Safe module to help catch some security issues you may miss.

grep

Just me, the boy and these two monks, no questions asked.