Course of Raku / Regexes and grammars / Regexes / Matching strings

The smartmatch operator

The operator that applies a regex to a string is the smartmatch ~~:

say 'the cat sat' ~~ /cat/; # ｢cat｣

A pattern written between slashes is the most common form, but there are two more that mean the same thing and are sometimes clearer:

say 'the cat sat' ~~ m/cat/;  # ｢cat｣
say 'the cat sat' ~~ rx/cat/; # ｢cat｣

The m/.../ form emphasises that you are matching, and is handy when you want to add options to the match (you will meet those options, called adverbs, later). The rx/.../ form constructs a regex value without matching it yet.

Very often you only care whether the string matched, not what exactly was found. Because a successful match is a true value and a failed match is false, you can use the result directly in a Boolean context. The cleanest way to get a plain True or False is the so function:

say so 'the cat sat' ~~ /cat/; # True
say so 'the cat sat' ~~ /dog/; # False

This makes a regex a natural condition for if:

if 'the cat sat' ~~ /cat/ {
    say 'found it';   # found it
}

Course navigation

← Matching strings   |   Quiz — Smartmatch →

💪 Or jump directly to the exercises in this section.