5 Responses to “Learning Perl Objects, References, and Modules”

1. Anonymous says:

   January 7, 2010 at 6:58 am

   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: 1 / 5

   [Reply]
2. Cory R. King says:

   January 7, 2010 at 7:45 am

   This book is perfect if you want to expand your perl horizon. It only gets 4 stars because, hey, I can’t give everything five stars.
   Rating: 4 / 5

   [Reply]
3. Tobias Eichner says:

   January 7, 2010 at 8:20 am

   “Perl Objects, References & Modules” written by Randal L. Schwartz is an overpriced, botched work that does not meet the quality of the first well-known “llama” book.

   Just 220 pages for such complex topics like OOP are simply too less allowing novice programmers to get familiar with. Many provided examples are highly complicated and lacking of good explanation.

   Sure, this book discusses advanced topics of Perl and therefore is also dedicated to the more experienced user, but it still is a book for people wanting to learn this great programming language – unfortunately they face a hard time when trying to do so.

   Well, Mr. Schwartz stated at the preface of this book that it was mainly written in a bar (with some beer, I guess). And yes, it reads like that…
   Rating: 1 / 5

   [Reply]
4. Anonymous says:

   January 7, 2010 at 10:56 am

   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: 5 / 5

   [Reply]
5. raul parolari says:

   January 7, 2010 at 1:38 pm

   This book attempts something very interesting: not just to describe “how” central aspects of Perl work, but also to understand the process of “how Perl got there”. Thus, the book does not serve the “conclusions” right away; it reaches them via a series of experimentations and improvements (in fact, similarly to what is done in other sciences).
   
   To make it interesting (and humorous but realistic at the same time) the book presents a band of “software sailors”, who write navigation software. They quickly discover the pleasures of workgroup development; they start reusing software with “eval” (on library files), they then limit unwanted effects with “do”, to finally adopt “require” to pull a file only once. Then, after chaos still erupts on name collisions (two different “turn_to_port” routines with the same name, which send one boat into a loop..), the sailors discover “package”, and finally, the fleet can proceed with a certain harmony [note: given the structure of the book, "use" will be introduced a lot later, in chapter 12].
   
   This is a very original software lesson; for anyone who reads chapter 2, it will be hard to see the line “package Xyz” and not smile remembering (at least once) the conflicts between Skipper & Gilligan. This is great teaching, as your mind associates a “scenario”, not just a “habit”, to a programming line.

   There are other chapters equally brilliant; more than the “Object” chapters, I liked especially the one on “Subroutine References”. It begins explaining how to reference a named subroutine, and it then builds a hash of sub references. Then, it prods us to do the next logical step (with a trick which recurs along the book: “why waste some brain cells to define a name for each subroutine, to only use it to initialize the data structure?”), gently pushing the reader to accept “anonymous” subroutines, code them in the hash structure itself, and enjoy the remarkable simplification of the code that results! The stage is now set to introduce “Callbacks”, and then “Closures”; again, with the same method of “one evolution at the time”:
   
   a) first a variable is declared to hold the callback, followed by a naked block with a private context and the callback assignment.
   
   b) then the code is simplified with a subroutine encharged to contain the variables on which the closure is done and to return the reference to the anonymous subroutine.
   
   c) last, it shows how the same subroutine can be invoked simultaneously, keeping its own context in every call.
   
   I must say that, after you begin to realize the power of “Closures” (I went back to read “Programming Perl”, p 260-262, to fully understand it), you regret that the only example given by the book is so elementary (findFile). Imagine instead, to remain with the sailors theme, a routine which computes a boat trajectory (closing on boat’s initial position, velocity, etc), and a main routine instantiating multiple boats and launching them in a race. Multiple automatas in action (with a few lines of code!); this would close the chapter in full glory.

   More than once you have the strange feeling that the book was written under a constraint of having less than 200 pages. Examples: it presents a remarkable lesson on Autovivification, but fails to alert against unvoluntary autovivifications (when testing structures for existence).
   
   Or see for, in chapter 2, the section “Packages and Lexicals” whose first line is: “A lexical variable isn’t prefixed by the current package because package variables are always global”. The statement is not false but it is so awkward at the start a section (“X does not have property Z, because only Y has Z”). Why not to spend a few pages, mentioning the Perl symbol table and on this basis explain concretely the difference between “lexical, global, local”? else, everything remains so abstract.
   
   Still, these are minor defects of an unique remarkable book. The introduction mentions that the material is built on the Stonehenge courses; for all of us without the opportunity to attend them, but able to read, think and experiment, this book is an excellent deal to “see” the Stonehenge people in action.
   Rating: 4 / 5

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