Oracle 21c

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CREATE TYPE CUSTOM_DATA IS TABLE OF VARCHAR2(4000);
DECLARE
  cust_data CUSTOM_DATA;
BEGIN
  cust_data:=CUSTOM_DATA('A','B','C');

  FOR i IN (SELECT COLUMN_VALUE as val FROM table(cust_data))
  LOOP
    DBMS_OUTPUT.put_line(i.val);
  END LOOP; 
END;
/
1 rows affected

dbms_output:
A
B
C

DECLARE
  cust_data CUSTOM_DATA;
  cur       SYS_REFCURSOR;
  value     VARCHAR2(4000);
BEGIN
  cust_data:=CUSTOM_DATA('A','B','C');

  OPEN cur FOR
    SELECT COLUMN_VALUE as val FROM table(cust_data);

  LOOP
    FETCH cur INTO value;
    EXIT WHEN cur%NOTFOUND;
    DBMS_OUTPUT.put_line(value);
  END LOOP; 
END;
/
1 rows affected

dbms_output:
A
B
C