Programming Perl, Second Edition is a reference work that covers nearly all of Perl, while Learning Perl 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.
Programming Perl, Second Edition (the Camel Book): ISBN 1-56592-149-6 (English)
Learning Perl (the Llama Book): ISBN 1-56592-042-2 (English) ISBN 4-89502-678-1 (Japanese) ISBN 2-84177-005-2 (French) ISBN 3-930673-08-8 (German)
Perl 5 Desktop Reference (the reference card):
ISBN 1-56592-187-9 (brief English)