I am also one who started with the online version of this book about two years ago. I tried the O'Reilly books first, but they were too complex and riddled with sarcasm that I didn't quite understand. I understand and appreciate it now, but it was an obstacle back then.
in reply to CGI Programming 101 - Perl for the WWW
After this course I had a basic foundation of the language under my belt which made it possible for me to get through the O'Reilly books. I never refer back to this book now - I only use Perl Monks and the Perl Bookshelf, but thank god I had an easy place to start gaining understanding about something that is very complex to someone with just a hobby computer education.
Because of my experience with it, I recommended this book as a good -introduction- to a friend recently, but then told him that after he finished the online version he should go through Ovid's CGI course to really learn safe practice.