The operator is called "smart-match". When you do: $a ~~ $b You are in fact doing: $b.ACCEPTS($a) So any object can determine how it will interpret

The operator is called "smart-match". When you do: $a ~~ $b You are in fact doing: $b.ACCEPTS($a) So any object can determine how it will interpret any other object in smart-matching. The core classes or course have all these methods implemented in the expected way. And you can easily do that for your own classes as well: class Foo { multi method ACCEPTS(Int:D $count) { $count == 42 } multi method ACCEPTS("frobnicate" --> True) { } } my $foo = Foo.new; say 42 ~~ $foo; # True say 666 ~~ $foo; # False say "what" ~~ $foo; # False say "frobnicate" ~~ $foo; # True