       ``"%-*.*s" % (10, 20, msg)`` becomes
            ``"%s" % (fill_exact_width(msg, 10, 20))``.

        ``"%20.10s" % (msg)`` becomes
            ``"%s" % (fill_exact_width(msg, 20, 10, left=False))``.

        ``"%s%.10s%s" % (pre, msg, suf)`` becomes
            ``"%s" % (fill_exact_width(msg, 0, 10, prefix=pre, suffix=suf))``.
        r4