m a m a n
m a m a n
n:let n:let n:let n:let n:let
m a m a n .
 ɛ m WORD_BOUNDARY a WORD_BOUNDARY  ɛ m WORD_BOUNDARY a WORD_BOUNDARY  ɛ n WORD_BOUNDARY
m WORD_BOUNDARY a WORD_BOUNDARY m WORD_BOUNDARY a WORD_BOUNDARY n WORD_BOUNDARY