my $t= parse XML::Twig::Elt(\*DATA);
$t->sort_children( sub {
	my $elt = shift;
	my $top = $elt->att('attribute');
	my $kid = sprintf '%04d', ($elt->first_child->tag =~ s/Child//r);
	return $top . $kid;
});
$_->print for $t->children;