$input is not meant for an event. Events are things that are going to happen whether or not you are there and aren't going to sit around and wait for you to type something. That said, there are ways around this. For example, using a timer...

.timer 1 1 echo -a This is my input: $!input(Press OK or Cancel)

Note that you do need the ! in there to prefer $input() from being done until after the timer triggers.

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