The Basics of Regular Expressions

Regex is, essentially, a whole new language, with its rules, its structures, and its quirks. You'll also find that your knowledge of most other programming languages will have practically no bearing on learning regex, for the simple reason that regular expressions are highly specialized and follow their own rules.

As defined by Kleene, the basic regex axioms are the following:

• A single character is a regular expression denoting itself.

• A sequence of regular expressions is a regular expression