Operators

Smartmatch ~~

Full

One operator that asks "does this match that?" against types, ranges, and more.

The smartmatch operator ~~ asks whether the left value matches the right, where "match" depends on what's on the right: a type tests membership, a range tests containment, a regex tests a pattern, a code block tests a predicate. It is the engine behind when, grep, and given.

Against a type #

say 5 ~~ Int;
say "x" ~~ Int;
say 3.5 ~~ Real;

Output

True
False
True

Against a range #

say 5 ~~ 1..10;
say 20 ~~ 1..10;

Output

True
False

Against a predicate #

A Callable on the right is called with the value; a WhateverCode makes a tidy inline test. (Parenthesise it so the * curries only the predicate, not the whole ~~ expression.)

say 5 ~~ (* > 2);
say 1 ~~ (* > 2);

Output

True
False

Notes #

The result is always a plain Bool (unlike a bare regex match, which returns a Match — smartmatch Booleanises it).
What "match" means is defined by the right-hand side's ACCEPTS method, so any type can define how it smartmatches.
when X is $_ ~~ X, and grep X keeps elements where $_ ~~ X — the same operator throughout, which is why ranges, types, and regexes all work in a when.