Course of Raku / Regexes and grammars / Regexes / Lookaround assertions / Lookahead
Quiz — Lookahead
What does the following program print?
say '5 cm' ~~ / \d+ <?before ' cm'> /;| 1 | ｢5｣ |
| 0 | ｢5 cm｣ |
| 0 | False |
| 0 | Nil |
The positive lookahead <?before ' cm'> requires
the digits to be followed by cm, which they are. The
assertion checks that text but does not consume it, so the match is just
the digits, ｢5｣.
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