I don't have experience with this module, personally, but I may have a need for it soon. Here is an example program using net::snmp: rping. Also, you are sending a string to the router which is of type OCTET_STRING as far as ASN.1 is concerned.

I am not sure how to stuff all of that into a single list value

This is just a way to describe the argument list to the sub. It appears that you want:

$server = "1.2.3.4";
$oid=".1.3.6.1.4.1.9.2.1.55.$server";
$session->set_request($oid, OCTET_STRING, "myfile");
[download]

HTH, --traveler