anchor.diff:      alert(a);
       return alert(b);
   } finally {
  -    if (undefined === prevMv2) {
  +    if ('undefined' === typeof prevMv2) {
           delete arguments['callee']['mv'];
       } else {
           arguments['callee']['mv'] = prevMv2;
  
positive.code:     alert(a3);
      return alert(b);
  } finally {
      if (undefined === prevMv2) {
          delete arguments['callee']['mv'];
      } else {
          arguments['callee']['mv'] = prevMv2;
  
negative.code:     var b = mv1[0];
      return a + b;
  } finally {
      if ('undefined' === typeof prevMv2) {
          delete arguments['callee']['mv'];
      } else {
          arguments['callee']['mv'] = prevMv2;
  