def parse_simple_expression_list(l):
    """
    This parses a comma-separated list of simple_expressions, and
    returns a list of strings. It requires at least one
    simple_expression be present.
    """

    rv = [ l.require(l.simple_expression) ]

    while True:
        if not l.match(','):
            break

        e = l.simple_expression()

        if not e:
            break

        rv.append(e)

    return rv