The incontestably definitive reference book on Perl, written by the creator of Perl and his apostles, is now in its second edition and fourth printing. Note that O'Reilly books are color-coded: turquoise (some would call it teal) covers indicate perl5 coverage, while magenta (some would call it pink) covers indicate perl4 only. Check the cover color before you buy!
Programming Perl (the "Camel Book"):
Authors: Larry Wall, Tom Christiansen, and Randal Schwartz
ISBN 1-56592-149-6 (English)
ISBN 4-89052-384-7 (Japanese)
(French and German translations in progress)
What follows is a list of the books that the FAQ authors found personally useful. Your mileage may (but, we hope, probably won't) vary.
If you're already a hard-core systems programmer, then the Camel Book just might suffice for you to learn Perl from. But if you're not, check out the ``Llama Book''. It currently doesn't cover perl5, but the 2nd edition is nearly done and should be out by summer 97:
Learning Perl (the Llama Book):
Author: Randal Schwartz, with intro by Larry Wall
ISBN 1-56592-042-2 (English)
ISBN 4-89502-678-1 (Japanese)
ISBN 2-84177-005-2 (French)
ISBN 3-930673-08-8 (German)
Another stand-out book in the turquoise O'Reilly Perl line is the ``Hip Owls'' book. It covers regular expressions inside and out, with quite a bit devoted exclusively to Perl:
Mastering Regular Expressions (the Cute Owls Book): Author: Jeffrey Friedl ISBN 1-56592-257-3
You can order any of these books from O'Reilly & Associates, 1-800-998-9938. Local/overseas is 1-707-829-0515. If you can locate an O'Reilly order form, you can also fax to 1-707-829-0104. See http://www.ora.com/ on the Web.
Recommended Perl books that are not from O'Reilly are the following:
Cross-Platform Perl, (for Unix and Windows NT)
Author: Eric F. Johnson
ISBN: 1-55851-483-X
How to Set up and Maintain a World Wide Web Site, (2nd edition) Author: Lincoln Stein, M.D., Ph.D. ISBN: 0-201-63462-7
CGI Programming in C & Perl, Author: Thomas Boutell ISBN: 0-201-42219-0
Note that some of these address specific application areas (e.g. the Web) and are not general-purpose programming books.