You may possibly be unable to run cgis at all, so I would suggest you make sure of that first. I would probably just ftp a very basic perl script first and see if that can be run, showing if cgi is enabled and if perl is installed.

#!/usr/bin/perl 
print "Content-type: text/plain\n\nworking\n";
[download]

For the other part of your post, I would say that yes, re-inventing wheels is something to try, but don't expect to actually use that code for anything you care about.

If you search all those posts about using CGI.pm, you can find links such as the list here. I suggest you read all of those related to cgi, including the full specs and you continue to search for more documents.

The CGI.pm module has support for these features missing in most parsers written:

• Multiple parameters with same name ?foo=hi&foo=blah
• File uploads with many files
• DOS attacks through long data uploads and the like
• A consistent interface
• Modularity
• Updateability (it's constantly scrutanized and updated for exploits in its code and cgi security in general)
• Scalability

And probably another hundred more that I can't think of but are needed if you want a fully safe and reliable cgi engine other than CGI.pm.