Effective Perl Programming, by Joseph Hall and Randal Schwartz, Addison Wesley, 1998
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[ISBN 0-20141-975-0] Sixty short lessons in aspects of Perl Language, drawn from the authors' teaching and consulting experiences, designed to add to the reader's understanding and bag of tricks. Performance characteristics of Regular Expressions, symbol tables and scoping, hints for debugging, brevity vs. readability trade-offs, etc. Clean, well considered examples. A practical adjunct to the standard Oreilly And Associates Perl texts.
This is a great bedside book. I've been reading a section a night, and my mediocre Perl skills increased noticeably after a week. -- Dave Smith
The author has much of the book online - check out www.effectiveperl.com 
(Broken Link? 2006-02-25) - but it certainly is worth buying the wood pulp. Makes for a quite orderly progression to the Advanced book. -- Peter Merel
Joseph Hall's blog: effectiveperl.blogspot.com . Chapters 1, 2, 3, 4, and 7 of the book are available online there.
See original on c2.com