How can I use this line: $string .= '.' if $string !~ /[.!?]$/; in the code below?

Change it to $message .= '.' if $message !~ /[.!?]$/; and just replace that whole block of code with that one line.

But really, you should listen to merlyn's admonition and refrain from deploying this script!

-sauoq
"My two cents aren't worth a dime.";