======Synopsis:======
[[on]] [<modes>]window [<serial#>] [-|^]<match> { <action> }

======Description:======
This hook is triggered whenever output to any window matches any
existing [[WINDOW]] hook.  Extreme care should be taken when using this hook
to redefine messages, as an [[ECHO]] command inside it will also be hooked
by it.

======Parameters:======
|$0 |reference number of name of the window|
|$1- |text printed to the window|