Sorry I miss you previous post so with the few elements I have
(500 error and a code snippet)
I can only provide a common guideline for solving error 500 problem :

• Check that the script compile (as tachyon pointed out)
  (use warnings and use strict and -T never hurt if you got some input)
  with perl -cw script.pl
• If your script was FTPed from a box with a different OS from the one running on the box where you're executing the script, check for added invisible character
  (EOL problem for DOS->UNIX transfer...)
• Check that the path to perl interpreter is correct
  (otherwise you'll get a error 500 page and a 'no such file or directory' in your web logs...)
• In all case check the HTTP server logs for more detailed error messages.

"Only Bad Coders Code Badly In Perl" (OBC2BIP)