I don't have much to add, except CGI::Session can use both Data::Dumper and Storable as well as FreezeThaw to freeze and thaw data.

By default it uses Data::Dumper, so that it doesn't require any seperate installations to get it working. However, the only disadvantage of using Data::Dumper over the other two data serializers is it doesn't do good job in thawing stored objects.

Storing objects in session data is not something one normally does, so Data::Dumper is usually just what you need.