If your USB device is a HID device and, I assume from the nature of your question, behaves like a disk drive, then it is a disk drive and you access it exactly as you would your hard disk. If it is a HID device then your software simply doesn't need to know that USB is involved.

However your references to Net::Telnet and suggestion that the device is some sort of test device imply that that is not the case. You really have to make it clear what the device is. I can understand that you don't wish to do that in a public forum such as this and offer an exchange of email as a way I may be able to help in a more focused fashion. I am not offering to write drivers or planing lecture 101 in implementing USB devices :).