LOL. Well, if Perry's campaign is the guilty party, it's spokesman can hardly cite another campaign "with evidence"!
Furthermore, Cain doesn't have to provide a source, not to the media, and not at this time. We don't know exactly the venue Cain might want to pursue.
Cain probably doesn't know what venue Cain might want to pursue. He just wants the spotlight on someone else, and since he hates Perry, that's where he's pointing it.