The info regarding the controlling of the motor and use of Win32::SerialPort is completely irrelevant to the problem you're asking about.

As has already been mentioned, your posted code does not include anything that would change/rest the value. I will repeat the request that Athanasius made. Please post a short but complete script that demonstrates the problem you're having with the setting/resetting of the values so that we can run some tests. With that info we should be able to point out problem and solution. It would also be helpful if you would use proper code formatting so that your code is more readable.