Maybe my module is really an extension to SQL::Abstract?

Maybe SQL::Abstract::Join? But I would only use that name is you truely were extending SQL::Abstract in some way to support joins. I think that SQL:: is a namespace which can be added too, but IMO SQL::Abstract:: should only be added to for things specific to or working with SQL::Abstract.

Can we see more of the API? It looks like a very interesting module, I am curious how it works, etc in a larger example.

And no, I dont know of anything like this on CPAN, then again, I either like to write my own SQL or use our in house OO Persistence tools.