What's New
To help you decide if it's worth your while to upgrade from the first edition, I wrote this article at the O'Reilly Network. It describes what's been updated (everything), and what's new (lots).

What's Not New
What hasn't changed is the exhaustive research that went into it, the attention to detail, the breadth and depth of coverage, and the careful typesetting. (I did all the production myself, typesetting every speck of ink on every page that has a page number.)

It's not "Just for Perl"
The first edition contained a 100-page chapter devoted to Perl, so many who merely glanced at it assumed it was a book on Perl regular expressions instead of the general book on all regular expressions that it was. The "Perl blue" cover perhaps helped reinforce that idea. However, let me assure you that while the Second Edition does have a huge chapter devoted to Perl, it has 350 other pages on general and language-specific topics (and an additional 50 pages for the table of contents and the index). The cover is still "Perl blue", but like before, the content aims at all regular expressions.

Table of Contents
The table of contents is available online. The page is sort of large (about 110k -- but hey, it's a big book!). It'll give you a good feel for what the book does and doesn't cover.

Back-Cover Sales Blurb
Here's the back-cover copy that's supposed to get you excited about the book.

Check It Out at Your Library
Ask for it at your library. Its ISBN is 0-596-00289-0.