Regular Expressions (regex) scalar function

The XMLQUERY function allows the user to use the 'fn:matches' XQuery function, which is great. Please see example UDF which does this...

~~~~~~~~~~
--#SET TERMINATOR !

CREATE FUNCTION "UDF_STRING_REGEX_MATCH"
( SEARCHSTRING VARCHAR (50)
)
RETURNS SMALLINT

DETERMINISTIC
NO EXTERNAL ACTION

BEGIN

DECLARE SQLSTATE CHAR(5) DEFAULT '00000';
DECLARE SQLCODE INTEGER DEFAULT 0;

DECLARE REGEX_RESULT SMALLINT DEFAULT 0;
DECLARE XMLDOC VARCHAR(60); -- 50 FOR DATA, 10 FOR XML TAGS

SET XMLDOC = '' || TRIM(SEARCHSTRING) || '' ;

-- Can't seem to get it to work using a variable for the fn:matches parm,
-- so this is what I have to do instead (hard coded regular expression)
-- which means I have to have many different such statements in my code
-- to cater for my various possible regular expressions - not good

SELECT 1
INTO REGEX_RESULT
FROM SYSIBM.SYSDUMMY1
WHERE XMLCAST(
XMLQUERY('fn:matches($D/DOC, "^1[0-9][0-9]")'
PASSING XMLPARSE(DOCUMENT XMLDOC) AS "D") AS INTEGER) = 1;

RETURN REGEX_RESULT ;

END!
~~~~~~~~~~~~~~~~~~~~~~

When I execute this, passing in a value of 123 as the input parameter, I get the expected result of 1 back because 123 matches the literal regular expression within the UDF. I see from this manual (http://www-01.ibm.com/support/knowledgecenter/SSEPEK_10.0.0/com.ibm.db2z10.doc.xml/src/tpc/db2z_fnmatches.dita ) that the “pattern is string literal”. The same is also true in DB2 z/OS Version 11.

This RFE is to request that 'pattern' be changed to allow for a VARIABLE or a literal, because allowing a literal only makes for a UDF which is not very generic. In order to be able to handle a number of desired regex patterns I would need to hard code a series of similar statements and conditionally execute the right one based on some other input variable. Even then of course, it would still require further coding changes to add more expressions in the future. It would be far easier (better?) if I could pass the regex expression into the UDF and use that variable as 'pattern'.

Better still would be a scalar function that allows for a REGEX match on a string using a pattern, without having to build an XMLDOC etc.

Thanks