#sentence-segmentation

A naive sentence splitter breaks the text after every ".", "?" or "!" that is followed by whitespace:

import re
txt = "Dr. Lee paid 3.50 euros for tea. She left at 5 p.m. on Monday. Was it worth it? Yes."
print(len(re.split(r"(?<=[.?!])\s+", txt)))

What does it print? (The text has 4 real sentences.)