Here's a nice list of some free and legal Perl books available on the web for your perusal. A few of these I've already pointed out, but they bear repeating. Especially in a nice and useful list format for your bookmarking pleasure:

• CGI Programming on the World Wide Web
• Perl 5 by Example
• Picking Up Perl
• Learning Perl the Hard Way
• Web Client Programming with Perl
• Extreme Perl
• Beginning Perl
• Perl for the Web
• Embedding Perl in HTML with Mason
• Practical mod_perl
• Perl 5 Internals
• Impatient Perl
• Perl Design Patterns