execTclM c e = do 
  (r,s) <- runTclM c e 
  case r of
    Right _ -> return s
    Left e -> error (show e)
execTclM c e = do 
  (r,s) <- runTclM c e 
  case r of
    Right _ -> return s
    Left e -> error (show e)
execTclM c e = do 
  (r,s) <- runTclM c e 
  case r of
    Right _ -> return s
    Left e -> error (show e)