How to loadblance Oracle DB by use irules to differentiate read and write request?

I want to use irules to differentiate oracle read and write request.

 

Who can tell me how to do it?

 

 

rule:

 

If request include "read ABC",then use db_read_pool

 

else if request include "write string" then use db_write_pool

 

 

I can not know what is the right syntax.pls help me,thanks.