If it is talkin'bout the letter "R" (thanks JazzO), I have never heard that, so I still "don't get it" or "I got nothin" (used interchangeably here on the north side) or for you out-of-towners "It means nothing to me" or "A comment at this point is belabouring the obvious"(a kind of "Why are we still talking about this?") -or- "you have so much more experience, therefore I have nothing worthwhile to say"(said completely facetiously)!
Take your pick!