execl ?-argv0 argv0? prog ?arglist?
              Do  an execl, replacing the current program (either
              Extended Tcl or an application  with  Extended  Tcl
              embedded  into  it) with prog and passing the argu-
              ments in the list arglist.

              The -argv0 options specifies that argv0  is  to  be
              passed to the program as argv [0] rather than prog.

              Note: If you are using execl in  a  Tk  application
              and it fails, you may not do anything that accesses
              the X server or you will receive a BadWindow  error
              from  the X server.  This includes executing the Tk
              version of the exit command.  We suggest using  the
              following command to abort Tk applications after an
              execl failure:

                  kill [id process]

              This command is provided by Extended Tcl.