Devel::Size might be useful, especially if you have some idea which variables/objects/data structures might be suspect.

Do you know why you've been told it's leaking? Assuming this is on a unix/linux box, can you try "top -p your_process_pid" and see if the VIRT figure grows in an unbounded way over time?

Edit: Didn't find it earlier, due to the odd name, but Devel::Gladiator looks promising. It walks everything, and gives an example of how to spot new entries.