{
    my %dat_by_id = ...;

    sub get_X_for_Y {
        my ($Y) = @_;
        state $map_Y_to_id = {
            map +($_->{Y} => $_->{id}), values %dat_by_id
        };
        return $dat_by_id{$map_Y_to_id->{$Y}}{X};
    }

    sub get_X_for_Z { ... }
    sub get_V_for_W { ... }
    ...
}