Koumas scored his second from the penalty spot in the 89th minute after McShane's clumsy challenge on Cotterill to give Wales some slight comfort from a disappointing campaign.
Perkins took a gamble in the 77th minute with a looped shot from 25 yards out and it took a slight deflection from Kennedy on its way into the net to turn the tie on its head - and into extra-time with the score locked at 3-3.
The Wolverines are still in this thanks to the Game of the Tournament let's give it a slight edge over FGCU's dumping of Georgetown a stunning final-minute comeback versus Kansas to secure overtime and eventually a win.