In Chapter 1, I explained that regular expressions are imperative. Imperative languages come with control structures. When developing software using a programming language, we use the following control structures:
Branching: In most programming languages, we use if statements and switches. In regular expressions, we branch off using the | metasyntax character or using character sets. An | structure vaguely corresponds to an if-else structure, and a character set vaguely corresponds to a switch statement. An example of character sets is [ab]. Read it like a|b. In other words, choose either a or b.
