gistfile1.pl

glitchmr@feather ~/examples> cat in
#!/usr/bin/env perl6
multi infix:<in>(Str $a, Str $b --> Bool) { so $b ~~ / $a / }
multi infix:<in>(Str $a,     @b --> Bool) { so $a eq any @b }
multi infix:<in>(Str $a,     %b --> Bool) { %b{$a}:exists   }

say 'ab'    in 'abc';
say 'cake'  in 'lolcakes';
say 'win'   in 'win';
say 'lol'  !in 'face';
say 'fin'   in ['a', 'b', 'fin', 'lol'];
say 'fi'   !in ['a', 'b', 'fin', 'lol'];
say 'a'     in {a => 'b'};
say 'b'    !in {a => 'b'};
glitchmr@feather ~/examples> /usr/bin/perl6 in
===SORRY!===
Cannot negate in because it is not iffy enough
at in:9
------> say 'lol'  !in⏏ 'face';
glitchmr@feather ~/examples>