IN comparison is not supported inside function, alternative ?

Hello,

I try to rebuild my Oracle functions inside HANA ( 1.00.85 ).

I have now a problem with my function:

CREATE FUNCTION SB_TEST(

  BUKRS NVARCHAR,

  VV001 DECIMAL,

  VV002 DECIMAL,

  VV003 DECIMAL )

RETURNS TEST Decimal(15,3)

LANGUAGE SQLSCRIPT READS SQL DATA AS

BEGIN

    test := case when :BUKRS in ('1010','1020') then 1

                 when :BUKRS in ('1600') then 2

                 else 0

            end;

END;

Error: feature not supported: IN comparison is not supported

Is there an alternative for IN comparison inside functions ?

Some of my functions uses more than 20 IN expressions.

Holger