

          If an unknown Tcl command is entered from the command line,
          then the Unix command path, specified in the environment
          variable PATH, will be searched for a command of the same
          name.  If found, the command will be executed.  This feature
          is provided to enhance the interactive environment for
          developing Tcl scripts. This is only supported from the
          command line, not in script files or in procedures, to
          eliminate confusion.  The exec or system command should be
          used to run Unix commands inside scripts.
