I would suggest:
1. buy book "Learning Perl" by Randal Schwartz and Tom
Christiansen - I believe there's a 3rd edition now. It's
an excellent primer, and it has a whole chapter on CGI
programming.
2. I did
perldoc -q cgi
and came up with this section:
Where can I learn about CGI or Web programming in Perl?
For modules, get the CGI or LWP modules from CPAN. For
+ text‐
books, see the two especially dedicated to web stuff in
+ the
question on books. For problems and questions related
+to the
web, like ‘‘Why do I get 500 Errors’’ or ‘‘Why doesn’t
+it run
from the browser right when it runs fine on the command
+ line’’,
see the troubleshooting guides and references in perlfa
+q9 or in
the CGI MetaFAQ:
http://www.perl.org/CGI_MetaFAQ.html
Also, I'd go to www.perl.com - look there. And go to google and search for "perl cgi tutorial" or something similar.
HTH.