REGEXP_SUBSTR Conversion

Hello Gurus,

I am trying to convert the following code from oracle:

SELECT DISTINCT REPLACE(SUBSTR (REGEXP_SUBSTR (code,'[^,]+',1,LEVEL),2,8),']','') code
FROM DUAL 
CONNECT BY REGEXP_SUBSTR (code, '[^,]+', 1, LEVEL) IS NOT NULL;

Please assist to convert it into some SUBSTR / INSTR combination or CASE function.

Thanks.

Regards,