Learning Perl By Randal L. Schwartz, brian d foy, Tom Phoenix

What is Perl? Perl is a general-purpose programming language originally developed for text manipulation and now used for a wide range of tasks including system administration, web development, network programming, GUI development, and more.
The language is intended to be practical (easy to use, efficient, complete) rather than beautiful (tiny, elegant, minimal). Its major features are that it's easy to use, supports both procedural and object-oriented (OO) programming, has powerful built-in support for text processing, and has one of the world's most impressive collections of third-party modules.
How to learn Perl? that is good a question. You can use "perldoc" command-line.
Example:

# perldoc -f chomp

If You are looking for the best way or some books with Perl programming language. If you are looking for what book as tutorial for you. Please check "Learning Perl, 6th (Making Easy Things Easy and Hard Things Possible) By Randal L. Schwartz, brian d foy, Tom Phoenix". You can read Free Sampler.
This book is updated for the lasted version (Perl 5.14) and It was the bestselling Perl tutorial since it was first published in 1993.

# perl -v
This is perl 5, version 14, subversion 1 (v5.14.1) built for x86_64-linux

Copyright 1987-2011, Larry Wall

Why I mention book titles "Learning Perl", You know this book (first edition) was published on the first day more than 15 years ago. It is written by someone who have many experiences on Perl Programming and Perl Contribution. On this book (sixth edition). I believe time be able to guarantee quality of book. What you see in this book? It has 17 Chapters. You will learn from Basic (something what should know about Perl) to Advance (Perl Techniques) and Exercise each chapter will help you for learning. You can use this book as reference.

This book has topics include:
- Perl data & variable types
- Subroutines
- File operations
- Regular expressions
- String manipulation (including Unicode)
- Lists & sorting
- Process management
- Smart matching
- Using third party modules

Twitter's Authors:
Randal L. Schwartz @merlyn
brian d foy @briandfoy_perl
Tom Phoenix