I would assume that you have already seen these, but it seems to me that Graph::Base and Meta::Graph::Directed might take you some steps in the right direction. As a tree-structure is a special case of directed graphs, it should not be too difficult to construct a tree using these modules. From the pod in Meta::Graph::Directed

This class is here to provide a place to add method to the Graph::Directed module available from CPAN. I know that Graph::Directed looks pretty nice but still if I need any convenience methods or maybe a small algorithm or two it will be nice to add them at the graph level.

Perhaps too bare-bones, but at least a suggestion. I haven't used the module myself, though, so administer the required grains og salt. Good luck :)

pernod
--
Mischief. Mayhem. Soap.