Mastering Regular Expressions by Jeffrey E. F. Friedl ISBN 1-56592-257-3 [1st edition January 1997] http://www.oreilly.com/catalog/regex/
Network Programming with Perl by Lincoln Stein ISBN 0-201-61571-1 [1st edition 2001] http://www.awlonline.com/
Object Oriented Perl Damian Conway with foreword by Randal L. Schwartz ISBN 1-884777-79-1 [1st edition August 1999] http://www.manning.com/Conway/
Data Munging with Perl Dave Cross ISBN 1-930110-00-6 [1st edition 2001] http://www.manning.com/cross
Mastering Perl/Tk by Steve Lidie and Nancy Walsh ISBN 1-56592-716-8 [1st edition January 2002] http://www.oreilly.com/catalog/mastperltk/