Use Decode?

Hi,

I have a table like this

Table Name: CONFIG_STR_T

STR_CODE

----------------

'MBU'

'MBD'

'MBT'

'MIN'

'FRE'

My Requirement: For the rows starting with MB i want the result to be displayed as 'MB' instead of its actual value. For the other records, I want their original values.

REQUIRED OUTPUT:

STR_CODE

----------------

'MB'

'MB'

'MB'

'MIN'

'FRE'

I tried using the following SQL:

select decode(str_code, regexp_like 'MB%', 'MB', str_code) from CONFIG_STR_T;

I am getting error while trying to execute this query. Please let me know which is the best way to get my required output. Also please enlighten on where I went wrong.