anchor.diff:  
     "(function () {
       var x1 = callMeOnce();
  +    __PS_MV_REG = [];
       return (Math.exp(x1) - Math.exp(-x1)) / 2;
   })();")
   
  
positive.code: var bar = function (y) {
      return 2 + y;
  };
  return bar(foo(1));
  })();")
  
  
negative.code:     (let* ((a (bar)))))
    "function foo() {
      var a = bar();
      __PS_MV_REG = [];
      return null;
  };")
  
  