Get id of a tuple using exception

Hello,
i'm using a pl/sql procedure and I prevent inserting duplicate tuples using an exception for example:

  BEGIN
       INSERT INTO "Triples"(id, subject, predicate, "object") 
                    VALUES (id, sub_i, pred_i, obj_i);
 EXCEPTION WHEN unique_violation THEN
                --do something.

In some cases I have interest in getting the id of the tuple that was already in the table when the exception is triggered. Is there a way for the EXCEPTION to return that id instead of using a select to know wich was the id of the triple already existing in the table?

Thanks, 
Filipe