Regular Expressions (Regex) are expressions that define a search pattern. Regex can be implemented in various tasks including searching, replacing, validation and text processing/parsing. It is mostly known in the combination with the programming language Perl, but Regex are also supported by most other languages. If you every want to really dive deep into the world of Regular Expressions, I'd recommend the book "Mastering Regular Expressions " by Jeffrey E.F. Friedl. Testing ...