Flush the   keyboard   buffer.

This reads characters from the keyboard input and
discards them until there are no more currently buffered,  
and then allows the program to continue.

The program must not wait for users to type anything.

$ wait 0::10  ! gives us 10 seconds to get keystrokes into the type-ahead buffer
$ on control_y then $ goto clean
$ set terminal /noecho
$ loop: read /prompt="" /time=0 sys$command /error=clean buffer
$ goto loop
$ clean:
$ set terminal /echo