this 2 elisp-functions do eval code of your source code the way tcl-eval-region does, but they prevent output by replacing ;;; with dummy code.


 (defun tcl-eval-region-no-output ()
   "my own tcl-eval-region,  
 before sending a region to the tcl-process
 this function replaces
           ;;;
 with 
           ;; set tcl-eval-no-output {} ;;
 in order to prevent unwanted outputs"
   (interactive) 
   (local-set-key (kbd "C-c C-r") 'tcl-eval-region-no-output)
   (let* ((proc (inferior-tcl-proc))
 	 (s1 (buffer-substring (region-beginning) (region-end)))
 	 (s2 (replace-regexp-in-string ";;;" ";; set tcl-eval-no-output {};;" s1)))
     (tcl-send-string proc s2))
   )
 
 (defun robert-tcl-eval-line-no-output ()
   "my own tcl-eval-line.
 before sending the tcl-code to the tcl-process
 it replaces
    ;;;   =>   ;; set tcl-eval-no-output {} ;;
 in order to prevent unwanted outputs"
   (interactive)
   (local-set-key (kbd "C-c C-l") 'tcl-eval-line-no-output)
   (let* ((proc (inferior-tcl-proc))
 	 (s1 (buffer-substring-no-properties (point-at-bol) (point-at-eol)))
 	 (s2 (replace-regexp-in-string ";;;" ";; set tcl-eval-no-output {};;" s1))
 	 (s3 (concat s2 "\n")))
     (tcl-send-string proc s3)
     (next-line))
   )