As lachoy has already said, you can use Tree::Simple for this. Of course, I wrote it so I favor it heavily. As for a persistence layer, I have actually implemented several different ones for Tree::Simple over the years, only one of which has been packaged for on CPAN right now, it is called Tree::Parser. Tree::Parser is more appropriate for serializing Tree::Simple heirarchies to files, but could be made to use a DBI backend by writing a custom filter.
If you would like to tell me a little more about your application, I can possibly help you out by giving you some persistence code I have already written (if it is appropriate to your needs). At the very least, I might be able to point you in the right direction.