my $xml_obj = XML::Simple::Tree->new(file => 'directory.xml',
                                       node_key => 'dir',
                                       target_key => 'name');

I have been studying the documentation for XML::Simple::Tree. But i am bit confused about node_key and target_key in the above code. Can anybody please tell me what node_key and target_key actually mean ? And what are values supplied to them ?