I voted for Programming Perl
(I've got the 2d edition), despite its information being largely replicated in the man pages. Since I program mostly for Windows, I needed to install Perl before I had access to the man pages;
Programming Perl gave me enough useful information to convince me to do that and enough information to get started. I also currently own
Learning Perl, which I found to be too basic,
Mastering Perl/Tk, which is specialized (and, in my opinion, it could be better organized), and
Perl Cookbook, which is handy when I want to
steal some codeget inspired to find a solution to a specific problem. I still find the camel book to be useful, in that it's frequently easier for me to use a book than online man pages (especially with my randomly-prone-to-demonstrate-why-I-hate-Windows workplace desktop).
emc
"Being forced to write comments actually improves code, because it is easier to fix a crock than to explain it. "
—G. Steele