One recieve message multiple send messages

Hi All,
How do I split an incoming message to different messages depending on a
property of a record in the incoming message.

Message can be as follows (single file)

12 ad jk ui
13 jk ui hh
12 gh as nh
13 nh jy ki

I want 12's to be a single out file and 13's to be another out file

Thanks
Sree