I agree with the previous poster, that the shutoff system should be a Big Red Button and not a keyboard.

(semi-off topic)

I had a somewhat similar problem in a C++ app. My program recorded audio and many people were recording long documents, not touching the keyboard/mouse while speaking and having the screen saver kick in. I fixed the problem by turning the screen saver off during recordings with the following Microsoft's Visual C++ code:

(turn off the screen saver)
SystemParametersInfo(SPI_SETSCREENSAVEACTIVE, FALSE, 0, 0)

(turn on the screen saver)
SystemParametersInfo(SPI_SETSCREENSAVEACTIVE, TRUE, 0, 0)

While that isn't perl code, it might be possible for Perl to make a similiar system call. I don't know, but I'm placing the information here anyways in case it might help somebody wants to start looking for another way to turn off the screen saver.