在PL / SQL Proc下面输出错误的输出

CREATE OR REPLACE PROCEDURE Proc_TEST(T_DATE DATE DEFAULT TRUNC(SYSDATE))
AS
  PREV1 VARCHAR(20);
  mnth VARCHAR(20);
BEGIN
SELECT TO_CHAR(TO_DATE(TRUNC(T_DATE,'MM')-1),'MON_YYYY')  INTO PREV1  FROM DUAL;
FOR i IN 1 .. 3 LOOP
  mnth:='PREV'||i;
  DBMS_OUTPUT.PUT_LINE('op'||mnth);
  DBMS_OUTPUT.PUT_LINE('op'||PREV1);
END LOOP;
END;
/
CREATE OR REPLACE PROCEDURE Proc_TEST(T_DATE DA