def apply_T6(word):
    '''If a VVV-sequence contains a long vowel, there is a syllable boundary
    between it and the third vowel, e.g. [kor.ke.aa], [yh.ti.öön], [ruu.an],
    [mää.yt.te].'''
    WORD = word
    offset = 0

    for vvv in vvv_sequences(WORD):
        seq = vvv.group(2)
        j = 2 if is_long(seq[:2]) else 1 if is_long(seq[1:]) else 0

        if j:
            i = vvv.start(2) + j + offset
            WORD = WORD[:i] + '.' + WORD[i:]
            offset += 1

    RULE = ' T6' if word != WORD else ''

    return WORD, RULE