Extended Tcl offers many of these types of functions.  For instance,
extended Tcl has the `signal` command:

        signal action siglist [command]

        where action is one of "default", "ignore", "error", "trap", "get",
        plus the POSIX "block" and "unblock" actions (available only on
        POSIX systems, of course).  Siglist is a list of either the symbolic
        or numeric Unix signal (the SIG prefix is optional).  Command is your
        error handler (or a simple {puts stdout "Don`t press *that* key!"}  :-)

"trap" does what you expect, and I find "error" and "get" to be
extremely useful in interactive programs which demand keyboard
traversal.

Extended Tcl also has things like fork, etc.

Answer by brad@NeoSoft.com (Brad Morrison).