Error in this code?

Question

hi friends,
when I run this code it is giving error as
Cause: FDPSTP failed due to ORA-01427: single-row subquery returns more than one row
ORA-06512: at "APPS.UPD_VAC", line 18
ORA-06512: at line 1
can some one suggest a solution pls
the table vac_table has a single column... and it has only 1 record right now
CREATE OR REPLACE package body APPS.upd_vac is
procedure upd_prc(p_err_buf out VARCHAR2
,p_ret_code out NUMBER)
is
l_attr varchar2(100);
l_attr1 varchar2(100);
l_attr2 varchar2(100);
l_attr3 varchar2(100);
l_attr4 varchar2(100);
begin
SELECT MAX(ATTRIBUTE18) INTO L_ATTR FROM PER_VACANCIES;
select (regexp_substr (l_attr, '.*C')) into l_attr1 from dual;
select regexp_replace(l_attr,'^.*C(.+)$','\1') into l_attr2 from dual;
select to_number(l_attr2)+1 into l_attr3 from dual;
select l_attr1||l_attr3 into l_attr4 from dual;
insert into vac_table
(select l_attr4 from dual);
UPDATE PER_VACANCIES SET ATTRIBUTE18 =(select attribute from kdd_vacancy)
where vacancy_id =(select max(vacancy_id) from per_vacancies);
commit;
end;
end;

Answer 1

CREATE OR replace PACKAGE BODY apps.upd_vac
IS
  PROCEDURE Upd_prc(p_err_buf  OUT VARCHAR2,
                    p_ret_code OUT NUMBER)
  IS
    l_attr  VARCHAR2(100);
    l_attr1 VARCHAR2(100);
    l_attr2 VARCHAR2(100);
    l_attr3 VARCHAR2(100);
    l_attr4 VARCHAR2(100);
  BEGIN
    SELECT MAX(attribute18)
    INTO   l_attr
    FROM   per_vacancies;
    SELECT ( Regexp_substr (l_attr, '.*C') )
    INTO   l_attr1
    FROM   dual;
    SELECT Regexp_replace(l_attr, '^.*C(.+)$', '\1')
    INTO   l_attr2
    FROM   dual;
    SELECT To_number(l_attr2) + 1
    INTO   l_attr3
    FROM   dual;
    SELECT l_attr1
           ||l_attr3
    INTO   l_attr4
    FROM   dual;
    INSERT INTO vac_table
    (SELECT l_attr4
     FROM   dual);
    UPDATE per_vacancies
    SET    attribute18 = (SELECT attribute FROM   kdd_vacancy)
    WHERE  vacancy_id = (SELECT MAX(vacancy_id)
                         FROM   per_vacancies);
    COMMIT;
  END;
END; 
(SELECT attribute FROM kdd_vacancy)must return only a single row
ATTRIBUTE18 is a scalar & can only accept one value; which is correct value FROM KDD_VACANCY?