hello,

i suggest that you read Chapter 12: Introduction to CGI (pdf format) from Beginning Perl by Simon Cozens, it will explain what CGI is about and introduce you to the great CGI module, then move to some advanced stuff like cookies, debugging and security
the whole book is well written and is freely available online

you may also want to look at Perl's another great offering for dynamic web content creation: mod_perl, it also has an online book, titled Practical mod_perl

... and another source of information is Perlmonks.org's Super Search :) we've all been there, so some of your questions may allready be answered