1. It has many typos and mistakes. Mistakes in a "teach yourself" book are particularly unacceptable.
2. The explanations are very tedious to read and not very good. If you have never programmed then these tedious explanations may be of some help to you, although better quality explanations of the language are available elsewhere. But if you're an experienced programmer looking to learn Perl then reading an explanation of how a while loop works over and over again will, to say the least, not be your cup of Java. This is especially strange since, as it said in the book, this book is written for readers with at least some programming experience. Furthermore, many of the explanations are so vague that they're practically useless. For instance, instead of giving an explanation about the local scope of a foreach loop variable, the author says "if it [the iterating variable in the foreach loop] doesn't exist prior to the loop, it'll stop existing after the loop. If it does exist prior to the loop, the foreach will just use it as a temporary variable, and then restore its original value when you're done looping. You can think of the foreach variable as a sort of scratch variable used solely to store elements, which is then thrown away when the loop's done." And I consider this to be a representative example of most of the explanations in this book.
3. This book is a bad reference. Many people buy programming books so that they can quickly read a few pages and learn some detail about some language feature. For this, the book is useless. There are many features that do NOT have a full explanation, only a partial one, and even these are often times strewn around the book so that you'll have to search for them. And personally, I can not use this book as a reference since I have doubts about the correctness of many of its explanations.
4. The author will MANY times give a vague description of a feature and then tell you to look at the Perl documentation for more details. This makes the book useless for a beginner (since they're just learning the language) and useless for someone who already knows the language and is using it as a reference (since then they may as well have just gone to the Perl documentation from the outset).
5. The example programs are not that well written. The quality of the example programs reminds me of something that I would have written when I had just a few years of programming experience.
6. The book tells you many times about what you're going to learn about later in the book, which gets annoying.
7. The author includes useless programming examples for some reason. Ex: "For example, here's a somewhat pointless for loop that creates an array, and then destroys it, backwards, printing the number of remaining (sic) and the array itself as it goes: [shows the code] I can't image what sort of Perl program would need this kind of loop, and because it iterates over a list it would probably make more sense as a foreach."
8. Mistakes such as not knowing when to use "that" or "which" are unacceptable for any author.
1. If you're a beginner and if you can stand reading through all of it then you will learn something about the Perl language and you will learn how to create a quick script (although as a word of caution, if you emulate this book's examples then your scripts likely won't be very good).
This programming book is among the worst that I have seen.
Overall, I wish that I had bought another book.