The following books are considered the best for learning Perl. I use them daily in my work. The main "bible" of Perl is Programming Perl by Larry Wall, the creator of Perl. He presents the language from his perspective.
Best for learning: Learning Perl 2nd Ed, O'Reilly press
Best Perl Reference/Overall: Programming Perl, O'Reilly Press
Good Reference, Idea Book: Perl Cookbook, O'Reilly Press
All these books are available at Amazon.com or through the Perl web site: www.perl.com
Why O'Reilly? Well, simply put, they write books on programming that are actually fun to read, and are full of tons of info. I suggest them for any project. Keep in mind, you MUST learn Perl BEFORE you decide to actually code a CGI application, it will really make a difference in your code and to your finished product.
Once you get good a PERL (give yourself a good week of practice and use), then you can start learning CGI. My recommendation would be to read the documentation on CGI.pm that comes with Perl itself. Once you understand the basics of Perl, it is by far best to learn how to perform tasks from the documentation Perl comes with, it builds your skill and confidence as a programmer.
Hope this helps.
------------------
Fred Hirsch
Web Consultant & Programmer