What's New in This Edition

The book you're holding is thicker than its previous edition of five years ago—about 200 pages thicker. New material is spread across more than 80 entirely new recipes plus over 100 existing recipes that were substantially updated since the first edition. You'll also find two new chapters: one on mod_perl, Perl's interface to the popular Apache web server; the other on XML, an increasingly important standard for exchanging structured data.

Growth in this book reflects growth in Perl itself, from Version 5.004 in the first edition to v5.8.1 in this one. Syntactic changes to the core language are nevertheless comparatively few. Some include the spiffy our keyword to replace the crufty use vars construct for declaring global variables, fancier forms of open to disambiguate filenames with strange characters in them, and automatic allocation of anonymous filehandles into undefined scalar variables. We've updated our solutions and code examples to reflect these changes where it made sense to make use of the new features.

Several of Perl's major subsystems have been completely overhauled for improved functionality, stability, and portability. Some of these are relatively isolated, like the subsystems for threading (see Recipe 17.14) and for safe signals (see Recipe 16.17). Their applications are usually confined to systems programming.

More sweeping are the changes to Perl and to this book that stem from integrated support for Unicode characters. The areas most profoundly affected are strings (now with multibyte characters) and I/O (now with stackable encoding layers), so Chapter 1 and Chapter 8 include new introductory material to orient you to these sometimes confusing topics. These chapters also provide the bulk of recipes dealing with those specific topics, but this fundamental shift touches many more recipes throughout the book.

Another growth area for this book and Perl has been the welcome proliferation of many highly used and highly useful modules now released standard with the Perl core. Previously, these modules had to be separately located, downloaded, configured, built, tested, and installed. Now that they're included in the standard distribution, that's all taken care of when installing Perl itself.

Some new core modules are really pragmas that alter Perl's compilation or runtime environment, as demonstrated in Recipe 1.21, Recipe 12.3, and Recipe 12.15. Some are programmer tools to aid code development and debugging, like modules shown in Recipe 11.11, Recipe 11.13, Recipe 11.15, and Recipe 22.2. Others augment basic operations available on core data types, like those shown in Recipe 2.1, Recipe 4.13, Recipe 4.18, Recipe 5.3, Recipe 8.7, and Recipe 11.15. Finally, the networking modules have at last made their way into the core distribution, as seen throughout Chapter 18. We've probably not seen the last of this inward migration of modules.