Only way the stock is overvalued is if you strip out the buy back plan. Frankly speaking its the only reason the multiple hasn't seen greater contraction. But by any other means the current multiple indicates that it is fairly to slightly undervalued.
Looks reasonably priced to me at 14 times earnings. Canada's costs will hurt a bit but then it should be off to the races. Standard & Poor rates it a Fair Value of 4, meaning it is a bit undervalued and projects a 12-month target of $80. It appears to be a near future winner if you are patient.
I suspect a down day with good volume will mark the end of the selling. The good side is TGT is buying back shares on a lower cost basis. With Canada accretive and outstanding shares down to 570 million, the stock will do well and the dividend will go up a lot. Just have to wait into 2013 to see it.
Long term TGT is setting up to be a mature super stock like MCD, KO, JNJ.