a.p6

say 'start';
multi sub trait_mod:<is>(Sub $s, :$foo){ {}
    say "⟨is foo⟩ has been called with ⟨$foo⟩ on {$s.WHICH}";
}
sub bar() is foo<oi‽> { {}
    say 'bar has been called'
}
bar();
# OUTPUT: «⟨is foo⟩ has been called with ⟨oi‽⟩ on Sub|47563000␤start␤bar has been called␤»