This is a list of common mistakes that people make when writing Perl scripts and suggestions on how to fix them. Included are general help tips on how to debug - very important particularly for beginners at programming.
Common Server Errors and Messages CGI and Perl / General Development
Find out what those server response codes like 401, 404, 500 mean. It can help you troubleshoot minor problems - knowing these are a must if you'll be working on programs that run on a server.