You will find the SNMP Object Navigator very helpful. It helps to determine which mibs is which and what it does.

Also, at some point you will have to look at the RFCs. Specifically RFC 3416 and RFC 1157.

To check the packets sent and received you can use Wireshark.

Lastly, Net::SNMP will block your application; if you need to do other tasks while Net::SNMP is waiting for a response, you can use POE::Component::Net::SNMP. This will especially help if your app has a UI.