This command sends <anything you want> in such a way that it can be caught by
ON HOOK "anything you want"
or any regular ON syntax. E.g. if you have
ON HOOK * echo one $* three
and you send
HOOK two
it will display "one two three" as the on is activated.
This is useful if you want to put a special hook in a script or
alias that you can act upon with an on/hook or ignore at will.