class MyOptions {
    has $.length = 10;
    has $.height;
    has @.names;
}

class MyClass {
    has MyOptions $.options = MyOptions.new;

    method modify(%changes) {
        $!options.=clone(|%changes);
    }
}

my MyClass $n.=new;
say $n.perl;
$n.modify({length => 42, names => ['Kai', 'Otto']});
say $n.perl;