Practice Makes Regexp

Many programmers hear the term "regular expressions" and run the other way. Sure, they're incredibly powerful and useful... but their syntax can make your head hurt.
Practice Makes Regexp doesn’t aim to teach developers regular expressions. This book assumes you know a little bit about regular expressions, but that you're not totally comfortable with them. Perhaps you forget the syntax. Or you don't quite understand grouping. Or you don't know when you would want to use such features as backreferences. What you need is practice, and that's what Practice Makes Regexp gives you. As you solve the problems, and read the explanations, you'll become more fluent and comfortable with regular expressions. The book has 50 exercises, along with solutions (in Python, as well as Ruby, JavaScript, and PostgreSQL), solutions, and extended explanations. One chapter concentrates on the Unix shell, and on using "grep" effectively.