Ok. First, if you want to know what CGI is, read an article at webign: Introduction to CGI. Then, as a more advanced user, read a more technical introduction to CGI at www.webteacher.com/perltour/perltour.htm. This is a PERL-specific introduction, but you will see how CGI operates.

The following resources will help you find or build the CGI scripts for guestbooks, mail forms, counters, trackers, etc.

www.cgi-resources.com/Programs_and_Scripts/Perl/
ww.cgi-resources.com is a very good source of scripts and utilities, and this direct link will take you to their PERL section. If you want to browse the whole site, simply go to www.cgi-resources.com.

reference.perl.com
The home of PERL, perl.com offers everything you wanted for PERL, most things are free, you can fetch the newest version of PERL, with all the documentation. Unfortunately, the site is not for beginners, there is no compiled version of PERL, you will have to actually download the source (!) of PERL, compile it yourself on a UNIX (!) machine and well... you have to use a UNIX machine to create/run/test scripts. But this link offers many resources on PERL/CGI, including a FAQ, documentation and God knows what else.

Perl documentation
Again, taken from perl.com, this links to the PERL documentation. If you think the documentation is too difficult to comprehend (I haven't read it, but I wouldn't be suprised if it is), you might opt to buy a book on CGI or PERL. The best (price and quality) are, it seems, published by O'Reily. You can find more info at www.perl.com.

agora.leeds.ac.uk/Perl/start.html
A tutorial for PERL. I haven't seen it, so no comment at the time.

http://www.netscape.com/newsref/std/cookie_spec.html
A specification for cookies. I am no cookie-professional, so cannot comment on the usefulness of the cookies. "Cookies" is a very wrong name, because it makes you think of something that is good and tasty, not bad and complicated. Basically, a "cookie" is a piece of information that is being passed from browser to server and from server to browser. You can get information on user's screen resolution, etc.

Resources Page. Although webIGN resources page does not provide specific information on CGI, there are many links you can visit to learn more about CGI.