he+em he+em he+em
he em he em he em ?
h ɛ WORD_BOUNDARY  ɛ m WORD_BOUNDARY h ɛ WORD_BOUNDARY  ɛ m WORD_BOUNDARY h ɛ WORD_BOUNDARY  ɛ m WORD_BOUNDARY
h e WORD_BOUNDARY e m WORD_BOUNDARY h e WORD_BOUNDARY e m WORD_BOUNDARY h e WORD_BOUNDARY e m WORD_BOUNDARY