import re


def _parse_value(text):
    """
    Parse a variable server value with optional units.

    Parameters
    ----------
    text : str
        The variable server text.

    Returns
    -------
    str, str (or None)
        A tuple containing:
            - The value.
            - The units, which may be None.
    """
    match = re.match(r"(?P<value>.*)(?: {(?P<units>.*)})", text)
    if match:
        return match.group('value'), match.group('units')
    return text, None