Regular expressions

A regular expression (sometimes shortened to “regex” or “regexp”) is a pattern that can match some set of strings, and optionally capture parts of those strings for further use.

You can use regular expression values with the =~ and !~ match operators, case statements and selectors, node definitions, and functions like regsubst for editing strings, or match for capturing and extracting substrings. Regular expressions act like any other value, and can be assigned to variables and used in function arguments.