thats what i thought too, and tried these changes:

foreach my $node($tree->findnodes('path')->get_nodelist(){
  if ($node->exists('path')){
[download]

and alternatively

my $node_list = $tree->find('path');
foreach my $node($node_list->get_nodelist()){
  if ($node->exists('path')){
[download]

I still get the same error..