sub Dump {
    my @opts;
    for my $option (@dump_options) {
        no strict 'refs';
        my $ref = \${$implementation.'::'.$option};
        push @opts, [ $ref =>
            defined($$ref) ? $$ref : ${"YAML::$option"},
        ];
    }
    local ${$_->[0]} = $_->[1] for @opts;
    return &{"$implementation\::Dump"};
}