The perceptor in a standard system

It should be noted that when a program changes the _perceptor_ in such a way that any of points 1-3 from the section [XY.3.2.1 The initial perceptor](https://github.com/ForthHub/fep-recognizer/blob/master/terms-and-datatypes.md#xy321-the-initial-perceptor) is changed, the system (or the system's state) become non standard, till these points are reverted.
