You are probably right. I started playing with this and it took longer than I thought so I did not get time to comment the code, I thought as I had written it I may as well post it. It answered at least one of the OPs questions, can perl do this ;)

The data structure is not exactly beginers stuff but as we did not have any spec for output I thought that was the easiest way to show that it can be done. Now we have an output spec I would (shall if I get time this evening) re-write it so it prints the data as it finds it removing the need for a Hash of Arrays of God knows what.

Cheers,
R.