Advanced Perl Programming, 2nd Edition

Preface

It was all Nathan Torkington’s fault. Our Antipodean programmer, editor, and O’Reilly conference supremo friend asked me to update the original Advanced Perl Programming way back in 2002.

The Perl world had changed drastically in the five years since the publication of the first edition, and it continues to change. Particularly, we’ve seen a shift away from techniques and toward resources—from doing things yourself with Perl to using what other people have done with Perl. In essence, advanced Perl programming has become more a matter of knowing where to find what you need on the CPAN,^[*] rather than a matter of knowing what to do.

Perl changed in other ways, too: the announcement of Perl 6 in 2000 ironically caused a renewed interest in Perl 5, with people stretching Perl in new and interesting directions to implement some of the ideas and blue-skies thinking about Perl 6. Contrary to what we all thought back then, far from killing off Perl 5, Perl 6’s development has made it stronger and ensured it will be around longer.

So it was in this context that it made sense to update Advanced Perl Programming to reflect the changes in Perl and in the CPAN. We also wanted the new edition to be more in the spirit of Perl—to focus on how to achieve practical tasks with a minimum of fuss. This is why we put together chapters on parsing techniques, on dealing with natural language documents, on testing your code, and so on.

But this book is just a beginning; however tempting it was to try to get down everything I ever wanted to say about Perl, it just wasn’t possible. First, because Perl usage covers such a wide spread—on the CPAN, there are ready-made modules for folding DNA sequences, paying bills online, checking the weather, and playing poker. And more are being added every day, faster than any author can keep up. Second, as we’ve mentioned, because Perl is changing. I don’t know what the next big advance in Perl will be; I can only take you through some of the more important techniques and resources available at the moment.

Hopefully, though, at the end of this book you’ll have a good idea of how to use what’s available, how you can save yourself time and effort by using Perl and the Perl resources available to get your job done, and how you can be ready to use and integrate whatever developments come down the line.

In the words of Larry Wall, may you do good magic with Perl!

Audience

If you’ve read Learning Perl and Programming Perl and wonder where to go from there, this book is for you. It’ll help you climb to the next level of Perl wisdom. If you’ve been programming in Perl for years, you’ll still find numerous practical tools and techniques to help you solve your everyday problems.

Contents

Chapter 1, Advanced Techniques, introduces a few common tricks advanced Perl programmers use with examples from popular Perl modules.

Chapter 2, Parsing Techniques, covers parsing irregular or unstructured data with Parse::RecDescent and Parse::Yapp, plus parsing HTML and XML.

Chapter 3, Templating Tools, details some of the most common tools for templating and when to use them, including formats, Text::Template, HTML::Template, HTML::Mason, and the Template Toolkit.

Chapter 4, Objects, Databases, and Applications, explains various ways to efficiently store and retrieve complex data using objects—a concept commonly called object-relational mapping.

Chapter 5, Natural Language Tools, shows some of the ways Perl can manipulate natural language data: inflections, conversions, parsing, extraction, and Bayesian analysis.

Chapter 6, Perl and Unicode, reviews some of the problems and solutions to make the most of Perl’s Unicode support.

Chap ter 7, POE, looks at the popular Perl event-based environment for task scheduling, multitasking, and non-blocking I/O code.

Chapter 8, Testing, covers the essentials of testing your code.

Chapter 9, Inline Extensions, talks about how to extend Perl by writing code in other languages, using the Inline::* modules.

Chapter 10, Fun with Perl, closes on a lighter note with a few recreational (and educational) uses of Perl.

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Acknowledgments

I’ve already blamed Nat Torkington for commissioning this book; I should thank him as well. As much as writing a book can be fun, this one has been. It has certainly been helped by my editors, beginning with Nat and Tatiana Apandi, and ending with the hugely talented Allison Randal, who has almost single-handedly corrected code, collated comments, and converted my rambling thoughts into something publishable. The production team at O’Reilly deserves a special mention, if only because of the torture I put them through in having a chapter on Unicode.

Allison also rounded up a great crew of highly knowledgeable reviewers: my thanks to Tony Bowden, Philippe Bruhat, Sean Burke, Piers Cawley, Nicholas Clark, James Duncan, Rafael Garcia-Suarez, Thomas Klausner, Tom McTighe, Curtis Poe, chromatic, and Andy Wardley.

And finally, there are a few people I’d like to thank personally: thanks to Heather Lang, Graeme Everist, and Juliet Humphrey for putting up with me last year, and to Jill Ford and the rest of her group at All Nations Christian College who have to put up with me now. Tony Bowden taught me more about good Perl programming than either of us would probably admit, and Simon Ponsonby taught me more about everything else than he realises. Thanks to Al and Jamie for being there, and to Malcolm and Caroline Macdonald and Noriko and Akio Kawamura for launching me on the current exciting stage of my life.

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^[*] The Comprehensive Perl Archive Network (http://www.cpan.org) is the primary resource for user-contributed Perl code.