Course of Raku / Regexes and grammars / Regexes / Alternations

Alternation

Separate two or more alternatives with a vertical bar |. The pattern matches if any of them matches:

say 'no thanks' ~~ / yes | no /; # ｢no｣

The pattern tried yes and no; the string contains no, so that is what matched.

You can list as many alternatives as you like:

say 'the sky is blue' ~~ / red | green | blue /; # ｢blue｣

Alternatives can be any sub-pattern, not just literal words — they may contain character classes, quantifiers, and captures. To keep an alternation together inside a larger pattern, group it with square brackets [ ], which group without capturing:

say 'cathouse' ~~ / [ cat | dog ] house /; # ｢cathouse｣

Here the alternation cat | dog is one unit, and it must be followed by house.

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