anchor.diff:  %%%   M, F, and A are all evaluated except that if M or F are unbound variables, they
   %%%   are implicitly quoted to become literal symbols
   %%% - (M:F A1 ... An) is equivalent to ((lambda M:F/n) A1 ... An)
  +%%% - (try ...) is the exception handling primitive, modelled after Erlang's try
   
   -module(es_parse).
   
  
positive.code:     _ ->
        erlang:throw({bad_quote, Tl})
    end.
  
negative.code:       parse_letrec(Tl, Env);
      'quote' ->
        parse_quote(Tl);
      'try' ->
        parse_try(Tl, Env);
      _ ->
        parse_call(Hd, Tl, Env)
    end.
  