To parse out sentences you could use punctuation marks as delimiters to the words function.
sentences = "The quick brown fox jumped over the lazy dog. Hello World! Where's Waldo?";
slist = words(sentences, ".!?");
print(slist);
nsentences = nitems(slist);
print(nsentences);
Output from the log window:
{"The quick brown fox jumped over the lazy dog", " Hello World", " Where's Waldo"}
3