ab babb babb babb babb
ab babb babb babb babb .
 a p WORD_BOUNDARY b a p p WORD_BOUNDARY b a p p WORD_BOUNDARY b a p p WORD_BOUNDARY b a p p WORD_BOUNDARY
a b WORD_BOUNDARY b a b b WORD_BOUNDARY b a b b WORD_BOUNDARY b a b b WORD_BOUNDARY b a b b WORD_BOUNDARY