Have you tried running it from the command line? If you are still getting a 500 error, it quite likely is due to a syntax error in your script. Whenever I tinker with one of my CGI programs I always run it quickly from the editor to see if I broke anything before trying it from a browser.

I also suggest turning on warnings and taint mode via

#!/usr/bin/perl -wT
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and enabling strict syntax checking like so

use strict;
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Taint mode is essential for security reasons, whereas the other things are just plain good for your development as a perl programmer. For more info on these, there is a wealth of information on this site (or just keep asking questions). You should also read 'perldoc perlsec' since you are writing CGI code.