Firstly, things that often cause Internal Server Errors:

• Wrong permissions on the .pl files. They should have 755 permissions. NOT 777, because that may cause some servers to refuse to run them.
• Incorrect hashbang. Most of the time, the default #!/usr/bin/perl is the correct one, but sometimes Perl is installed elsewhere. In that case, you will have to find out where, and change the hashbang. On Windows servers, it should often be changed to #!perl.
• Incorrect options set up for CGI scripts. The configuration for the directory should contain Options +ExecCGI and AddHandler cgi-handler .pl. SOMETIMES, but definitely not always, this can be put into the .htaccess file. See the next point.
• A broken .htaccess file. Spelling errors, trying to use modules that are not installed, or trying to use options that have been forbidden elsewhere will all cause Internal Server Errors.
• An incorrect mod_suexec install. Mod_suexec is very temperamental, and getting it to allow running of Perl scripts at all is very hard. Don't ask me, I have no idea how to configure it.

>>7

Perhaps you should try reading >>1-4?