This is not a direct answer to your question of object persistance, but you may also want to check out the PageKit
application server project. It handles session management, authentication, form validation and prepopulation, page caching, nice templating and XML support (useful for cobranding, localization or dual HTML/WAP page generation among other things) along with a variety of other features in a mod_perl environment. It basically glues together a number of Perl web tools in a nice package.
The documentation is sparse, but my experience with it is that once you get everything figured out, it is rock-solid, lightning fast, and very extensible. Particularly to Perl developers who otherwise don't want to think about the sundry details of an application server. My experience with it has been very positive.
Hope this helps!