anchor.diff:  
   eval_ast({ast, type, self, children, []}, Env) ->
     #{ self := Self } = Env,
  -  Env#{ret_val => Self};
  +  erruby_rb:return(Self, Env);
   
   eval_ast({ast, type, str, children, Children}, Env) ->
     [SBin|_T] = Children,
  
positive.code: 
  pop_frame(Frame) ->
    #{ret_val := RetVal, prev_frame := PrevFrame} = Frame,
    PrevFrame#{ret_val := RetVal}.
  
  default_env() ->
    {ok, _ObjectClass} = erruby_object:init_object_class(),
  
negative.code:             not_found -> erruby_object:find_const(erruby_object:object_class(), Name);
              _ -> LocalConst
            end,
    erruby_rb:return(Const, Env);
  
  
  eval_ast(Ast, Env) ->
  