$ cat test_input.txt
Hello, world!
I said, "Hello, world!".
Did he say "Hello, world!"?
We're not sure.
1tab:   2tabs:          3tabs:                  END-TABS
# multi-spacing here - blank  line   next

The cat sat on the mat.
Old pronouns: thou; thee; thy; thine.
New pronouns: "u", 'ur'.
Forecastle = "fo'c'sle" or "fo'c's'le"
Forecastle = 'fo'c'sle' or 'fo'c's'le'
Don't hide the Very pistol; it could be very important.
Why exclude different but include same?