Some consider Perl to have a steep learning curve. I would say that it's not so much steep but it is a little long. But so far, for pipeline work, script/binary execution, file parsing/hacking, and string and array manipulation, I've found Perl to be excellent, and there are a lot of back doors that make it easy for me to accomplish the tasks I want to. As a note, I'm observed most people's confusion seems to stem from:
I've had a lot of help though. Here's a few books that I have learned from.
Learning Perl [SCHW97] covers the basics if you are completely unfamiliar with the language. It's a good intro, and I'm glad I read it as my first Perl, but now I am comfortable enough with the language that I never refer to this book anymore. I would recommend this as your first Perl book. I actually skimmed through the second edition recently, and it is pretty much how I remember it. Schwartz explains concepts in a logical order. I think his examples tend to be Sys Admin oriented.
The Perl Pocket Reference [VROM00] is a very concise summary of Perl. Functions are grouped by functionality. If you've programmed Perl already for a little while, this book is invaluable. I refer to this book all the time these days. You should have this on hand for reference, but you're not going to learn anything from it.
Programming Perl [WALL00] is of course the definitive reference. I consider myself to be very good at Perl scripting, and I still refer to this book on an almost daily basis. However, it is not a book to learn from if you're new to programming.
The Perl Cookbook [CHRI98] gives a lot of little 3-liners that do some common tasks. After you've coded for a litte while, this is a very useful book. For that matter, if you are a beginner, then having the examples in this book will probably help illuminate some of the wackier things you can do with Perl, and is a good learning aid. It is especially good if you have a copy of Programming Perl handy so you can verify for yourself what the details of the commands are, as the Cookbook describes a sublety, much like having a dictionary on hand while you read difficult literature. In fact, I would recommend this as a second Perl book to read after you've read "Learning Perl".
Advanced Perl Programming [SRIN97] is a good "next step" once you get comfortable with perl4 concepts. This was my introduction to Perl/Tk, and also helped me a lot with the foundations of references, then typeglobs and namespaces, then object-oriented related stuff. It is advanced though, so you really should program Perl for a little while first before diving into this.
The Perl Journal - http://tpj.com - a whole magazine dedicated to Perl. How can that be anything but a good thing? Honestly, I haven't directly used much from these articles. However, I've indirectly used them in that they've sometimes given me ideas, or made me aware of another library that's out there, or might have even explained a more fundamental concept. It's also a source of news in the Perl community. After you've programmed for a while and are mildly aware of the standard library, it wouldn't be a bad idea to read this. I hope they're still published. I haven't seen a Winter issue yet.
Linux Magazine - http://www.linux-mag.com - this of course focusses more on Linux, but they have a column, "Perl of Wisdom." In the ones I've read, they're written by Randal Schwartz, who also wrote "Learning Perl," and they've been very informative. I just recently discovered this column, and I found that some of them echo some of the concepts I've been meaning to write about. (In a couple subtle points, my personal style of using Perl will disagree with Schwartz, but one of the beauties of perl is that it supports multiple styles...)
There are few other web sites out there worth mentioning that have good coverage of Perl news:
I have also learned a lot from my co-workers. In particular, Mark Hammel and Rasmus Tamstorf have taught me a lot, and given me my starts into arbitrary structures and the Standard Perl Library. I have also had some productive discussions with Doug Cooper and Chris Allen about various Perl topics.
In my notes, I really do make an honest effort to credit my sources. But in case I neglect to, I got a lot of my tricks from the above sources.