help needs in converting db2 function in postgresql.

Hi,
I need helping converting following db2 function in postgresql function.
Any pointer will be great help in proceeding me ahead.

CREATE FUNCTION in_liststring ( string CLOB(64K) )
RETURNS TABLE ( ordinal INTEGER, index INTEGER )
LANGUAGE SQL
DETERMINISTIC
NO EXTERNAL ACTION
CONTAINS SQL
RETURN
WITH t(ordinal, index) AS
( VALUES ( 0, 0 )
UNION ALL
SELECT ordinal+1, COALESCE(NULLIF(
-- find the next delimiter ','
LOCATE(',', string, index+1), 0),
LENGTH(string)+1)
FROM t
-- to prevent a warning condition for infinite
-- recursions, we add the explicit upper
-- boundary for the "ordinal" values
WHERE ordinal < 10000 AND
-- terminate if there are no further delimiters
-- remaining
LOCATE(',', string, index+1) <> 0 )
SELECT ordinal, index
FROM t
UNION ALL
-- add indicator for the end of the string
SELECT MAX(ordinal)+1, LENGTH(string)+1
FROM t
;

commit;

DROP FUNCTION INSTRTBL;

CREATE FUNCTION INSTRTBL ( string CLOB(64K) )
RETURNS TABLE ( INSTRTBL CLOB(64K) )
LANGUAGE SQL
DETERMINISTIC
NO EXTERNAL ACTION
CONTAINS SQL
RETURN
WITH t(ordinal, index) AS
( SELECT ordinal, index
FROM TABLE ( in_liststring(string) ) AS x )
SELECT SUBSTR(string, t1.index+1, t2.index - t1.index - 1)
-- the join below makes sure that we have the lower and
-- upper index where we can find each of the ',' delimiters
-- that are separating the INSTRTBL. (For this, we exploit
-- the additional indexes pointing to the beginning and end
-- of the string.)
FROM t AS t1 JOIN t AS t2 ON
( t2.ordinal = t1.ordinal+1 )
;