Course of Raku / Regexes and grammars / Regexes / Literals and character classes

Matching literal text

The simplest pattern is a sequence of letters and digits. Such a pattern matches exactly those characters, in that order, anywhere in the string:

say 'the cat sat' ~~ /cat/; # ｢cat｣
say 'Hello'       ~~ /ell/; # ｢ell｣

The match does not have to start at the beginning of the string — the regex engine looks for the pattern at every position until it finds it.

A successful match produces a Match object. That ｢cat｣ in the first example is what such an object looks like when printed: say displays a Match as the text it matched, wrapped in the corner brackets ｢ ｣. If the pattern is not present, the match fails instead: the smartmatch produces Nil, an undefined value that counts as false in a boolean test:

say ('the cat sat' ~~ /dog/);       # Nil
say ('the cat sat' ~~ /dog/).Bool;  # False

Inside a regex, spaces are not significant by default — they are there only to make the pattern readable. So / ell / matches exactly what /ell/ would; the surrounding spaces are simply ignored:

say 'Hello' ~~ / ell /; # ｢ell｣

Because a space in the pattern is ignored, matching an actual space takes quotes: anything you put in quotes is matched literally. That same quoting is how you match a punctuation character that would otherwise have a special meaning in a regex:

say 'a b'       ~~ / 'a b' /; # ｢a b｣
say 'price: $5' ~~ / '$' /;   # ｢$｣

(For whitespace you can also use the \s class, which you will meet shortly.)

Course navigation

← Literals and character classes   |   Character classes →

💪 Or jump directly to the exercises in this section.