p6.p6

class Thingie {
    subset MoreNarrow of Str where {True};
    multi method stuff (MoreNarrow $ where /meows/) {
        say "Meow meow!";
    }
}

class SubThingie is Thingie {
    subset LessNarrow of Any where {True};
    multi method stuff (LessNarrow $ where /foos/) {
        say "Just foos...";
    }
}

SubThingie.new.stuff: 'meows and foos';