This flag is only applicable if calling a function. seEval will then call the function as a constructor, i.e. as new Func() rather than Func(). The this you pass is usually NULL, in which case a blank version of the object type is created for the constructor, the default behavior when you do a new Func(). You can make the this something else in which case the constructor will get it. Watch out, this may confuse constructors. Also, some constructors ignore the provided object and create their own.