Programming Perl, Second Edition is a reference work that covers nearly all of Perl, while Learning Perl, Second Edition is a tutorial that covers the most frequently used subset of the language. You might also check out the very handy, inexpensive, and compact Perl 5 Desktop Reference, especially when the thought of lugging the 676-page Camel around doesn't make much sense. Mastering Regular Expressions, by Jeffrey Friedl, is a reference work that covers the art and implementation of regular expressions in various languages including Perl.
Programming Perl, Second Edition (the Camel Book):
ISBN 1-56592-149-6 (English)
Learning Perl, Second Edition (the Llama Book):
ISBN 1-56592-284-0 (English)
Perl 5 Desktop Reference (the reference card):
ISBN 1-56592-187-9 (brief English)
Mastering Regular Expressions (the Hip Owl Book):
ISBN 1-56592-257-3 (English)