I second the recommendation by nysus. In fact, I learned Perl from the Camel Book,¹ which, despite being a reference work, is fun to read (in the early chapters).

I also made (and still make) extensive use of the free documentation at http://perldoc.perl.org/. Work through perlintro and the various tutorials (especially perldsc), familiarise yourself with the FAQs, and study perlsyn, perlref, and perlre. When I’m coding, I have this Perl documentation open in a browser window at all times.

The Perl Cookbook is now rather dated, but it’s still useful as a guide to well-written Perl code.

¹Programming Perl by Tom Christiansen, brian d foy & Larry Wall with Jon Orwant, currently in its 4^th Edition (2012).

Hope that helps,