This book is out of print, but it has been made available online through the O'Reilly Open Books Project . It really depends on what you are trying to do. The CGI modules should generally be used for heavy-duty CGI scripts.
Most modules have manpages embedded within the module itself.
These modules allow you to create and decode forms as well as maintain state between forms. It is a glorious Perl 5 version of cgi-lib.pl . I don't know O-O programming.