Mastering Regular Expressions by Jeffrey Friedl
CGI Programming with Perl by Gundavaram, Guelich & Birznieks
And, (re-inforcingly, or emphatically or somesuch):
For General Reference, to me (YMMV, as demonstrated above), the "Little Black Book," Perl Core Language, is indeed right up there with perldoc... . I can cheerfully forgive its omissions (I mean, c'mon, how many times does one need to hear the USUW mantra?) and even those few sins of commission ascribed to it.
And I'd go a lot of places without my Amex card that I would not go without my copy of the Pocket Reference to the "Perl Debugger".