How to capitalize first letter of first word in a sentence?

Question

I am trying to write a function to clean up user input.

I am not trying to make it perfect. I would rather have a few names and acronyms in lowercase than a full par

Answer 1

This:

Output:
abc. def! ghi? jkl.
abc. Def! Ghi? Jkl.

Note that you do not have to escape .!? inside [].