Scene 1, Layer 'actions', Frame 1, Line 1084: Syntax error: expecting identifier before plusassign.

    butt.addEventListener (MouseEvent.MOUSE_UP, makeMC);     var mc1:MovieClip = new MYMC();     function makeMC (event:MouseEvent):void {      if (clipAdded) {  // same as if (clipAdded == true) removeChildAt(numChildren - 1);  // last one added }     addChild (mc1);   clipAdded = true; mc1.x = += 100; mc1.y = 300; mc1.play(); clipAdded = true; } removeChildAt(numChildren - 1); }   }     var clipAdded:Boolean = false;     /*function Child (mc1){ clipAdded = true; }*/