When looking at a sizable existing project for the first time, does anyone know of a tool for Perl that you can run on the codebase and have it spit out summary information, ex. which classes inherit from which, which methods are overloaded, etc.? Or maybe even something to produce a diagram to help visualize the structure of the project?

I'm not sure what you'd call this. A "class browser", "object browser", or just CASE tool I suppose. Seems like it would be a time-saver when getting up to speed with a new project.

Currently, if faced with a pile of Perl code has no design docs ([sigh] serenity now, serenity now, ...), I just slog through each file, and use pencil & paper to come up with something to help visualize the system (though in the past have cobbled together crude tools to help with this, like grepping for "package", "use", and "sub").