```python
def sort_third(l: list):
    """This function takes a list l and returns a list l' such that
    l' is identical to l in the indicies that are not divisible by three, while its values at the indicies that are divisible by three are equal
    to the values of the corresponding indicies of l, but sorted.
    >>> sort_third([1, 2, 3])
    [1, 2, 3]
    >>> sort_third([5, 6, 3, 4, 8, 9, 2])
    [2, 6, 3, 4, 8, 9, 5]
    """
    # Extract values at indices divisible by 3
    third_values = [l[i] for i in range(len(l)) if i % 3 == 0]
    # Sort those values
    third_values.sort()
    # Build the result list
    result = []
    idx = 0
    for i in range(len(l)):
        if i % 3 == 0:
            result.append(third_values[idx])
            idx += 1
        else:
            result.append(l[i])
    return result
```