Log when the proxy home_server has no response

Dear all, we have some statistical requirements for eap-sim, I want know if I can identify and log it when we proxy Access-Request/Access-Challenge to external AAA home_server but no response back(timeout)? We now using perl to write our radius logs, so it would be great if we can identify "timeout" as response type and get the value from perl Hash - %RAD_* or somewhere outside by unlang. Is that possible? Best Regards, Okis