Como inserir na tabela temporária ao percorrer uma string - Oracle - PL/SQL

SQL> CREATE GLOBAL TEMPORARY TABLE tt_temptable(
  2        RowNums NUMBER(3,0) GENERATED ALWAYS AS IDENTITY,
  3        procNums  NUMBER(18,0)
  4    ) ON COMMIT PRESERVE ROWS;

Table created

SQL> 
SQL> DECLARE
  2    inputString  VARCHAR2(50) := '12,13,14,15';
  3  BEGIN
  4      INSERT INTO tt_temptable(procNums)
  5         SELECT REGEXP_SUBSTR (inputString,'[^,]+',1,LEVEL) ProcNums
  6           FROM dual
  7        CONNECT BY  REGEXP_SUBSTR (inputString,'[^,]+',1,LEVEL) IS NOT NULL;
  8  END;
  9  /

PL/SQL procedure successfully completed

SQL> SELECT * FROM tt_temptable;

ROWNUMS            PROCNUMS
------- -------------------
      1                  12
      2                  13
      3                  14
      4                  15

SQL> ALTER TABLE tt_temptable MODIFY( RowNums Generated as Identity (START WITH 1));