Sort::Tree implements a mechanism for sorting a list of objects into a tree structure and flattening it back into a list. Among other things, this is useful for displaying database queries in hierarchical views, such as nested categories, parent-child relationships, threaded discussions, and so forth. Trees have a lot to do with Graph theory, so if this module doesn't suit your fancy, have a look at the Graph:: Perl modules for an academically oriented implementation that employs vertex, edge, and node operations. For more information on how to use the perl module, see the pod documentation via the command perldoc Sort::Tree or, after installation, view the man pages with man Sort::Tree WWW: http://search.cpan.org/dist/Sort-Tree/