Convert Base64 text to ACSII text in an Inline Oracle SQL Statement

We store certain multilingual strings in Base64 in an Oracle Table. In order to select from that table, I had to convert the field to an ASCII string. Here is the syntax I used (Oracle 10g):

-- If null string, do not try to convert.
-- Trim string to 2000 characters (limit of CAST_TO_RAW)
SELECT DECODE(string_text,'','',UTL_RAW.CAST_TO_VARCHAR2(UTL_ENCODE.BASE64_DECODE(UTL_RAW.CAST_TO_RAW(substr(string_text,1,2000))))) AS first_2000_characters,
(case when length(string_text) > 2000 then DECODE(string_text,'','',UTL_RAW.CAST_TO_VARCHAR2(UTL_ENCODE.BASE64_DECODE(UTL_RAW.CAST_TO_RAW(substr(string_text,2001,2000))))) end) AS second_2000_characters
FROM my_table