How to use [strings.regex-replace]

The reference page of strings.regex-replace has its arguments, constraints and declaration.

Replaces matches of the given regular expression with some static sequence of characters.

// Results in "FOO bar hansen"
strings.regex-replace:foo bar hansen
   .:fo+
   .:FOO

The first argument is what regular expression to match, the second argument is what to replace all matches with.