Can you look in your Web server's error log to see what error message you're getting?

If it's a resource issue, running

  ulimit -a
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from your Perl script or a short shell script run as a CGI program might give you some insight.

In fact, why don't you run this as a CGI script and see what you get?

#!/bin/sh -x

printf "Content-type: text/plain\n\n"
exec 2>&1
id
ulimit -a
env
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This often gives me great clues in fixing CGI scripts.

Another trick is to write a short wrapper for your script to see what errors it's getting:

#!/bin/sh -x

printf "Content-type: text/plain\n\n"
exec 2>&1
/path/to/your/CGI/script
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Installing this as a CGI script and running it will display all output from your program in plain text format, including any errors it generates.