Trying to recreate ISNUMERIC() function but am getting an error

Hi,

I am writing a procedure to recreate a SQLSERVER function ISNUMERIC  in HANA SP4 as:

CREATE PROCEDURE  ISNUMERIC_ALEX (
      IN N VARCHAR(255),
      out L_RETURN VARCHAR(1)
  ) LANGUAGE SQLSCRIPT AS
/* Returns 'T' if the value is NUMERIC 'F' otherwise */
l_temp float;
L_RETURN VARCHAR2(1) := 'T';
BEGIN
  DECLARE MYCOND CONDITION FOR SQL_ERROR_CODE 592;
  DECLARE EXIT HANDLER FOR  MYCOND L_RETURN := 'F';
  SELECT to_integer(:N), 'T' INTO l_temp, L_RETURN FROM DUMMY;

END;

I am getting an error on compilation:

Could not execute 'CREATE PROCEDURE ISNUMERIC_ALEX"( IN N VARCHAR(255), out L_RETURN VARCHAR(1) ) ...'

SAP DBTech JDBC: [7]: feature not supported: The error code is not allowed in handler.

In the SP4 Manual there is an example for a trigger:

CREATE TRIGGER MYTRIG_CONDITION
AFTER DELETE ON TARGET

BEGIN
     DECLARE MYCOND CONDITION FOR SQL_ERROR_CODE 301;
     DECLARE EXIT HANDLER FOR MYCOND SELECT ::SQL_ERROR_CODE, ::SQL_ERROR_MESSAGE FROM DUMMY;
     INSERT INTO MYTAB VALUES (1);
     INSERT INTO MYTAB VALUES (1);  -- expected unique violation error: 301
     -- not reached

END;

What am I doing wrong?

Thanks,

Alex Vaynberg