Here are two things that should help immensely with debugging your CGI scripts...

First, before you upload your script to the web server, make sure it compiles: perl -c myscript.cgi

Second, use CGI::Carp to get more useful output when your script dies: use CGI::Carp qw/ fatalsToBrowser /; CGI::Carp by itself will produce nicely formatted error messages in the server's error log. Importing fatalsToBrowser will cause those errors to be sent to the browser as well.

You can also use CGI::Carp's carpout method to create your own private error log in an easily accessible place, rather than using the server's.