A wise hacker said: Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems. Regular expressions are a powerful tool in our hands and a first class citizen in ruby so it is tempting to overuse them. But knowing them and using them properly is a fundamental asset of every developer. We'll see hands-on examples of proper Reg Exps usage in ruby code, we'll look at bad and ugly cases, and learn how to approach writing and debugging them.