Learning Perl, 4th Ed.

Craig Maloney writes "Just about everyone out there who has ever typed #!/usr/bin/perl has encountered Learning Perl (otherwise known as "The Llama Book") in one form or another. You may have learned some of the intricacies of the language from this tome, or you've seen someone recommend this book to potential Perl programmers on-line. Learning Perl is generally in the top three recommended books for new Perl programmers, next to Programming Perl ("The Camel Book"). Now in its fourth edition, Learning Perl returns with updates covering the stable 5.8 series of Perl. The changes are subtle, but the improvements make for a clearer and more readable book." Read on for the rest of Maloney's review. Learning Perl, Fourth Edition author Randal L. Schwartz, Tom Phoenix and brian d foy pages 304 publisher O'Reilly rating 9 reviewer Craig Maloney ISBN 0596101058 summary The fourth edition of the classic text for learning the Perl language.

When I was initially introduced to Perl, I was one of those who was recommended to read Learning Perl. I picked up the initial edition (with the mauve binding), and began my journey into Perl. What I found was a dense, hard-to-follow introduction to the language, with the experienced Perl programmer in mind. I realized that the tutelage of this experienced programmer/author might be useful, but I opted for other books instead. As others looked to me for book recommendations, I recommended other works for people looking to immerse themselves in Perl, and relegated Learning Perl to the section of my library where live books with a steep learning curve (similar to the learning curve experienced by many with Kernighan and Ritchie's classic The C Programming Language). Like The C Programming Language, however, a full grasp of the language is not achievable from texts where the central focus is to avoid using the lingo and customs of those who are more familiar with the language. Only by full immersion in the culture of the language can one become fully proficient in that language. What's new? Learning Perl 4th edition has been updated in several ways from the previous edition. The text has been updated to reflect Perl 5.8, although this book doesn't introduce any 5.8 specific concepts. The new edition was reorganized from the previous version. The chapter on Regular Expressions is enhanced, and file handles are introduced in the I/O Basics chapter. CPAN is introduced in Learning Perl, since it has become much more important to beginners. The chapter on flat-file databases (DBM/DBM Hashes) didn't make the cut for this edition, but a good portion of the chapter made its way into Chapter 9 (Processing Text with Regular Expressions). The book has a cleaner feel to it, and flows without the erratic feel of the previous editions. What's good Learning Perl could rightly be called A Tourist's Guide to the Perl Culture. The material is immersive, and teaches Perl using the verbal language of a Perl programmer. No attempt is made to dumb down the material. This leads to sentences in the book like the following: Alas, these aren't words as you and I are likely to think of them; they're those \w-type words made up of ordinary letters, digits, and underscores. The \b anchor matches at the start or end of a group of \w characters. The previous sentence makes perfect sense for those who have already grasped the fundamentals of regular expressions, but for those who aren't quite up to speed, the previous sentence warrants further study. This can be a blessing or a curse for some. Ultimately, it forces the reader to understand the Perl culture which can only improve the reader's understanding of Perl. Also of note are the footnotes. Almost every page in the book contains footnotes commenting (sometimes sarcastically) about the topic at hand. Sometimes the footnotes can be distracting, as your eyes will busily look for the next humorous footnote, such as this little gem: And /,{5}chameleon/ matches "comma comma comma comma comma chameleon". By George, that is nice. What's Bad The only complaint I can level at Learning Perl is that there could be more explanation for some of the concepts in the book. In the section called "More Regular Expressions," the book presents the following example:

Here's the text:

I'm talking about the cartoon with Fred and Wilma!

And here's a substitution to remove those tags. But what's wrong with it?

s#(.*)#$1#g;

The problem is that the star is greedy. What if the text had said this instead?

I thought you said Fred and Velma, not Wilma

In that case, the pattern would match from the first to the last , leaving intact the ones in the middle of the line. Oops! Instead, we want a non-greedy quantifier. The non-greedy form of star is *?, so the substitution now looks like this:

s#(.*?)#$1#g;

And it does the right thing.

Unfortunately the less astute reader may not understand what exactly happened here. One line of output with the end result would help clarify what this regular expression did.

What's in it for me? Learning Perl would rightly be regarded as one of the classic texts for Perl programmers to read through at least once in their Perl careers. The book is chock-full of useful information, and even experienced Perl coders would do well to at least leaf through the pages of this book for paradigms to help their coding. Absolute beginner programmers would likely find this text a little over their heads, but intermediate programmers will find Learning Perl a valuable resource in their road to proficiency with Perl. You can purchase Learning Perl, 4th Edition from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.