anchor.diff:      macroexpand_1(S, Eenv, Benv);
   eval_internal(['macroexpand-all',S], Eenv, Benv) ->
       macroexpand_all(S, Eenv, Benv);
  +eval_internal([set|Args], Eenv, Benv) ->	%Set variables in shell
  +    set(Args, Eenv, Benv);
   eval_internal(_, _, _) -> no.			%Not an internal function
   
   %% c(Args, EvalEnv, BaseEnv) -> {yes,Res,Env}.
  
positive.code:     Imps1 = foldl(Fun, Imps0, Fs),
      St#slurp{imps=store(Mod, Imps1, St#slurp.imps)}.
  
  %% safe_fetch(Key, Dict, Default) -> Value.
  
  safe_fetch(Key, D, Def) ->
  
negative.code: 	{yes,Value,Env1} -> {Value,Env1};
  	no ->
  	    %% Normal evaluation of form.
  	    {lfe_eval:expr(Eform, Env0),Env0}
      end.
  
  %% eval_internal(Form, EvalEnv, BaseEnv) -> {yes,Value,Env} | no.
  