I do like a lot of the online resources, including
Ovid's tutorial, but sometimes I'm really pedantic and like to have an actual book in front of me.
I'd recommend
CGI Programming with Perl, 2nd Ed from O'reilly (please forgive me, but I can't remember the author ATM). Chapter 9 is about security, including taint checking with
-T. It also gives some great general advice, and demonstrates various styles of creating your CGI scripts (such as using the CGI module via a functional or OOP style interface, or having CGI generate your HTML versus using a here doc)
~Brian
