r.water.drain

Users,
  I must be missing something conceptually or software wise . . .
  I am trying to find the drainage basin above a point in a stream. I can not
get r.watershed to do this and it does not seem to be intended to. Though
r.water.drain is in my on-line manual and looks like it is exactly what I need,
the program itself is not in my grass version 4.1. Should it be? Is it a
contributed program that I need to compile? Or, is there another way to go
about this. Thanks ! ! !
     Morris