I said any kind I know of, but then I am renowned for being an uneducated thick-wit who won't listen to advice of my elders and betters.

I'm going to have to have a good think about what you've put there above. Digestion should be complete in a few days, before which any comment I make will probably be seen as another example of my stupidity.

The first thing that is running through the vacuous hole I refer to sometimes laughingly as my brain, is how to decompress this :

 

 my @nodes = (
 bless( {
    'data' => 'c',
    'tag'  => bless( {
      'data' => 'b',
      'tag'  => 'a'
    }, 'Node' )
  }, 'Node' )
);
[download]

From the source;

<<a>b</a>c</<a>b</a>>
[download]

I have a pathological aversion to all things OOP, but the apparent simplicity of what you have shown above is strangely appealing. Thanks!