for my $dir_node ($root->findnodes('//ncp_directory')) {
   my $dir_name = $dir_node->getAttrribute('name');
   for my $file_node ($dir_node->findnodes('ncp_file')) {
      my $md5       = $file_node->getAttribute('md5');
      my $file_name = $file_node->getAttribute('name');
      ...
   }
}