http://purl.org/tcl/home/man/tcl8.4/TkCmd/event.htm
Tested to work on Windows:
event generate <Alt-F4> ;# sudden death, somehow like [exit]
However, other Alt-(initial) events don't work when called from event, only from the keyboard.
Also see "event-oriented programming".
Tk syntax help - Arts and crafts of Tcl-Tk programming - Category Command