Simplistic use of "on_request_close", to prevent App from Exiting

[D. Xenakis]

Could someone please provide us here with a simple working script using "on_request_close" (preventing app from closing)?
I am trying to monitor Exit button from top bar, but no luck.

Thx!

[D. Xenakis]

I also just realised that using "on_request_close" monitors only ESC keyboard button and not Exit top bar button like I hoped.
Again, maybe I am doing something wrong.
Is there any way I can monitor Exit button.?
Any simplistic script available?

Thx