[etc]

move = function(addX,addY) {
   mc._x += addX;
   mc._y += addY;
}
arr = [{obj:arrowUp_btn,addX:0,addY:-1},{obj:arrowDown_btn,addX:0,addY:1},{obj:arrowLeft_btn,addX:-1,addY:0},{obj:arrowRight_btn,addX:1,addY:0}];
for (i = 0;i<arr.length;i++) {
   o = arr[i];
   o.obj.i = i;
   o.obj.onRelease = function() {
        move(arr[this.i].addX,arr[this.i].addY);
   }
}
delete i;
delete o;