my %nodes = ();
foreach my $tuple (split ',', $s) {
	# shorter spliting
	my ($child, $parent) = split ' ', $tuple;

	# init nodes if not already done
	$nodes{$child} ||= { node => $child, children => []};
	$nodes{$parent} ||= { node => $parent, children => []};

	# insert relationship
	push @{$nodes{$parent}{children}}, \$nodes{$child}
	$nodes{$child}{parent} = $parent;
}