Can enumerators modify public script variables?

How do you change that variable, can you paste some code? Because you absolutely can change stuff in enumerator, it's like a regular method in this regard

Can you maybe post a code example? An Enumerator is still "just" a function and does not scope differently than any other.

 private int _myNumber = 0;
 
 void Start() {
     StartCoroutine(IncrementNumber(_myNumber));
 }
 
 IEnumerator IncrementNumber(int num) {
     int localNumber = num;
     while (true) {
         yield return new WaitForSeconds(1);
         localNumber++; // Will not change the passed _myNumber at all
         _myNumber++; // Changes the declared _myNumber directly
     }
 }