Well, that's a tricky situation. If you punish false rape accusers, then they'll be dissuaded from admitting it was false rape and the accused will continue to rot in jail.. so that's why they don't punish them. I guess it also intimidates women from telling when they actually were raped, which they're intimidated enough from doing already.

But if those factors didn't matter and we were going to punish them for some reason, I'd say... rape!! no j/k =( i dunno. Prison time, of course.