

          The string result of a command typed at the Tcl shell
          command prompt is normally echoed back to the user.  If an
          error occurs, then the string result is displayed, along
          with the error message.  The error message will be preceded
          by the string ``Error:''.

          The set command is a special case.  If the command is called
          to set a variable (i.e. with two arguments), then the result
          will not be echoed.  If only one argument, the name of a
          variable, is supplied to set, then the result will be
          echoed.
