     COMMAND RESULTS
          Each command produces two results:  a  code  and  a  string.
          The   code   indicates   whether   the   command   completed
          successfully  or  not,  and  the  string  gives   additional
          information.  The valid codes are defined in tcl.h, and are:

               TCL_OK              This is the normal return code, and
                                   indicates    that    the    command
                                   completed successfully.  The string
                                   gives the command's return value.

               TCL_ERROR           Indicates that an  error  occurred;
                                   the    string   gives   a   message
                                   describing the error.  In  additon,
                                   the  global variable errorInfo will
                                   contain human-readable  information
                                   describing   which   commands   and
                                   procedures were being executed when
                                   the  error occurred, and the global
                                   variable  errorCode  will   contain
                                   machine-readable  details about the
                                   error, if they are available.   See
                                   the   section   BUILT-IN  VARIABLES
                                   below for more information.

               TCL_RETURN          Indicates that the  return  command
                                   has  been  invoked,  and  that  the
                                   current  procedure  (or   top-level
                                   command  or  source command) should
                                   return  immediately.   The   string
                                   gives  the  return  value  for  the
                                   procedure or command.

               TCL_BREAK           Indicates that  the  break  command
                                   has  been invoked, so the innermost
                                   loop should abort immediately.  The
                                   string should always be empty.

               TCL_CONTINUE        Indicates that the continue command
                                   has  been invoked, so the innermost
                                   loop  should  go  on  to  the  next
                                   iteration.    The   string   should
                                   always be empty.
          Tcl programmers do not normally need to think  about  return
          codes,  since TCL_OK is almost always returned.  If anything
          else is returned by a  command,  then  the  Tcl  interpreter
          immediately  stops  processing  commands  and returns to its
          caller.  If there are several nested invocations of the  Tcl
          interpreter  in  progress,  then  each  nested  command will
          usually return the error to its caller, until eventually the
          error  is  reported  to the top-level application code.  The
          application will then display  the  error  message  for  the
          user.

          In a few cases, some commands will handle certain  ``error''
          conditions  themselves  and  not  return  them upwards.  For
          example, the for command checks for the TCL_BREAK  code;  if
          it occurs, then for stops executing the body of the loop and
          returns TCL_OK to its caller.  The for command also  handles
          TCL_CONTINUE  codes  and  the  procedure interpreter handles
          TCL_RETURN codes.  The catch command allows Tcl programs  to
          catch  errors  and  handle  them  without  aborting  command
          interpretation any further.
