Your right. Letting the language do it is the right way to do it. What I am doing (using Clone) is to localise subtree's of the data structure into my'd vars at any given level of recursion and then allowing perl to undo this as it unwinds. See Re: Re: Deepcopy of complex structures. for somewhat more verbose (though not necessarilly clearer explanation :)

With regard an example of the structure. If I ever get the algorithm to work and if it works as well as I hope, I'm sure to post the code here.

If it doesn't I'll probably keep real quiet about it:)