iRules - How to send HTTP Response to a HTTP Pool by HSL

We want to send both request and response to a HTTP pool via HSL.

We could able to send request succesfully by below iRule

when CLIENT_ACCEPTED {       

               set hsl_test [HSL::open -proto TCP -pool clone_test_pool]  

    }

when HTTP_REQUEST_DATA {

 set request_cmd "HTTP::request"

 when HTTP_REQUEST_DATA {

 HSL::send $hsl_test "[eval $request_cmd][HTTP::payload]" 

}

But we are not able to send HTTP Response in similar fashion like below.

when HTTP_RESPONSE {

 set response_cmd "HTTP::response"

 when HTTP_REQUEST_DATA {

 HSL::send $hsl_test "[eval $response_cmd][HTTP::payload]" 

}