Rating:  - disenting opinion
I don't know why it is so hard to get a decent book on Perl. Every author seems to have a weird idea on how to present material. Perl programmers often seem to be devoted to the culture and celebrities of Perl. Randal Schwartz is perhaps the best of Perl authors.
This is a decent book but I don't particularly like the style. He teaches by example, ie he walks through an example, once you have understood this useless example he introduces a new point and you are supposed to have your interest raised and leap into the instruction part enthusiastically. Personally I don't like this style, give me the facts and *follow* up with examples. I don't want to waste my time wadding through a story that I can forget in 5 minutes, it also makes reviewing the material difficult.
Having said that the examples are good. Many books get very abstract and terse. Gilligan and his boat and coconuts is easier to relate to 'foo' which is a pointer to a scalar called 'bar'.
You need to sit down quietly and spend time reading this. I am a harried administrator and I don't have much time.
Rating:  - Review of Learning Perl Objects, References and Modules
Last Fall I attended a session on object oriented programming with Objective-C. When discussing various languages with object oriented capabilities, the speaker remarked, "Don't even talk to me about Perl." Many people feel that way about Perl without even having to talk about object oriented programming.
Randall Schwartz and Tom Phoenix, the authors of the Perl primer "Learning Perl", take on the task of talking about Perl and object oriented programming. Since Perl does not have object orientation as its principal structure, they have a significant task to pull off.
In the Foreword of "Learning Perl Objects, References and Modules" Damian Conway draws attention to Perl's particular magic in implementing object oriented programming: "[Perl] takes a collection of Perl's existing non-OO features...and then--with nothing up its sleeve--manages to conjure up fully functional objects, classes and methods."
This particular nature of Perl shows up in the nature of the book's content. "Learning Perl Objects, References and Modules" is not about why or when to use object oriented programming in Perl. It is about how to magically turn references and anonymous data structures into object oriented programming. In that way, it is more of a tactical book than a strategic book. The history and concepts behind object oriented programming are touched on only lightly in its 180 pages; however, the book follows a steady progression to the goal of making and distributing Perl modules.
Eagerly anticipating the publication of the book, I bought it as soon as it was available. I reaped immediate benefit from the first few chapters as they demonstrated how to accomplish the goals I had for a project that I was working on. I lost interest shortly after chapter 4. The book has sat on my coffee table for most of the last year. I paused for a great deal partly due to the vagueries of my personal life, but partly due to the odd pacing of the book. Without being able to give explicit examples, I can say that the book feels like a first edition.
The book seems squarely targeted at a point between "Learning Perl" and "Advanced Perl Programming." And that's where I'm at. It certainly has helped me develop the ability to use more complex data structures in my Perl programs. However, it is not a thorough discussion on object oriented programming. If you've grown beyond "Learning Perl", you may find "Learning Perl Objects, References and Modules" worth talking about.
Rating:  - Difficult on chapter 4 but fun
I wanted to learn about Perl objects and this book is not for me. I need an easier book for me (thats just me)
I cant study the material at all once I got to Chapter 4.
I feel degraded and stupid because I read all the good reviews.
The examples are good until Chapter 4. After that the code is fun to read and learning is not all hard with just some effort. Very scary indeed though on Chapter 4! I think most of the readers here have already a C background.
Its not the book is bad but very strange indeed on Chapter 4.
The part where the author talks about auto vivication is very strange because there is no mention of how you should analyze the data nor any code example. I got scared and have lost my confidence trying to learn perl. I honestly just dont like
Chapter 4; and all the time I have tried to decipher what the author is trying to teach. I just love to waste my time when Im not working and sitting here for 5 hours trying to figure out the example, however the book is to be read and Im sure I'll figure out the difficulties! So take time to read this book. Those are just the examples I found that I did not appreciate.
Rating:  - Great book for beginners and pros
This book does a great job on helping you grasp the concepts of objects and oop related concepts. I already know perl well, and use daily as part of my job. But I'm so used to procedural programming that I sometimes forget the details about oop. This book helps remind me about oop, and I try to use the examples here when coding new stuff :)
Rating: - Perfect book for taking your Perl skills to the next level
In the world of Perl there was once only the 'camel book,' held in perhaps as much reverence as 'K & R' among C programmers. It certainly appealed to roughly the same audience, those who wanted a short, sharp introduction to a programming language. It was with a problem that needed solving and a copy of the camel book that I started as a Perl programmer.
Then for those that wanted a introduction to Perl and programming Randal L. Schwartz wrote Learning Perl, a book that has arguably become the definitive textbook for teaching Perl. The one weakness was that it left off before really getting to the guts of building large, complex projects in Perl. It did not cover classes, objects, breaking your code up into pieces or the more arcane aspects of variables, references. For this we had to resort to the last few chapters of the 'camel book' and I, for one, have never really been totally comfortable at this end of the language; when I'm reading someone else's code it might take a couple of reads to fully understand the process.
Now this weakness has been well and truly addressed. Schwartz, with Tom Phoenix, has written "Learning Perl Objects, References & Modules", a volume that takes the same steady approach to teaching you the more advanced topics as the earlier 'Learning Perl'. Schwartz has spent the years since writing 'Learning Perl' teaching and writing. You can tell, this is a superbly written book, not that 'Learning Perl' wasn't well written; it's just that this volume is far better.
The Guts
The book starts with a chapter on building larger programs that covers @INC, eval, do and require before discussing packages and scope. It then has several chapters on references that explains in well understandable fashion and increasing complexity all the ins and outs of references including dereferencing, nested references, references to subroutines and references to anonymous data before a final chapter on references that gives you some incredibly useful tricks such as sorting and recursively defining complex data.
The book continues with three chapters that give you a solid grounding in Perl objects. Here Schwartz has assumed that you know at least a little about object oriented programming, some may feel the need for more explanation of concepts might be required, but if you've had any experience in OOP before then the clear examples and descriptions here are probably all you want.
Modules are not as well covered, with only a single chapter, but it is hard to think of anything left out, it covers using them and building your own so well that it left me wondering what all the fuss was about, "seems obvious to me." The book concludes with chapters on building a distribution out of your module, testing it using make test (with Test::Harness), Test::Simple and Test::More before a chapter telling you how to contribute to CPAN.
Each chapter of the book concludes with a number of small exercises, designed to be done in just a few minutes, that cement the learning of the previous chapter. The answers to these are at the end of the book.
Conclusion
Once I'd finished I felt I had a much more solid grounding in Perl, certainly I was much better able to understand another programmer's code that dealt with such things as subroutine references and some complex data structures. While the subject matter of this book is almost entirely covered in 'Programming Perl' the tutorial aspects of this book made it much easier going. The style would be familiar to anyone who has read 'Learning Perl', light without being frivolous and extremely well written, Schwartz seems a master at reducing complexity to manageable bites.
This book is deceptively easy to follow, each new idea built onto earlier ones, each new language concept introduced in an easy manner. The writing is excellent, it's hard to explain why I appreciated it so much. That may be the reason, the writing isn't forced or heavy or too light or obvious. It just allows the solid material of the book to shine through. Go to the ubiquitous O'Reilly website and grab the example chapter (the site also has a few Errata, the Table of Contents and the code from the book) and give it a look.
I think this may well become a classic, I may well in ten years time talk of Schwartz's books with the same awe I now talk of Brian Kernighan's. I'll certainly eagerly await his next book and keep this one close until it comes. Oh, and Randal, how about 'Software Tools for Perl Programmers'?
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