meters:
    - ``expr`` - expression that must match zero or more times
    - ``default`` (optional) - value to be returned if the optional expression is not found.

    Example::

        # US postal code can be a 5-digit zip, plus optional 4-digit qualifier
        zip = Combine(Word(nums, exact=5) + Opt('-' + Word(nums, exact=4)))
        zip.run_tests('''
            # traditional ZIP code
            12345

            # ZIP+4 form
            12101-0001

            # invalid ZIP
            98765-
            ''')

    prints::

        # traditional ZIP code
        12345
        ['12345']

        # ZIP+4 form
        12101-0001
        ['12101-0001']

        # invalid ZIP
        98765-
             ^
        FAIL: Expected end of text (at char 5), (line:1, col:6)
    rą