Finding where one sentence ends and another begins is trickier than might be imagined. Enter a regexp that matches all the items in the first column (positive examples) but none of those in the second (negative examples).

Positive	Negative
assumes word senses. Within does the clustering. In the but when? It was hard to tell he arrive." After she had mess! He did not let it it wasn't hers!' She replied always thought so.) Then	in the U.S.A., people often John?", he often thought, but weighed 17.5 grams well ... they'd better not A.I. has long been a very like that", he thought but W. G. Grace never had much