As it stands, MouseGetPos should return the position of the mouse cursor, and while I understand the motivation of returning x, y, hwnd, and control to minimize delay, multiple return types are not implemented, so both SplitPath and MouseGetPos are troublesome when a single line is required. (Unless JS destructuring will be implemented, {hwnd} := MouseGetWin())
Actually, I think adding A_MouseHwnd as an alternative to A for getting the current window under the mouse would be a very useful built in variable. Considering that MouseGetPos returns 3 arguments, two of which are actually "positional".