I'm not an expert at Convert::ASN1 but I've used it in Net::SNMPTrapd. You may want to have a look at that for an example?

I think you have to create a decode using the prepare() method. That's what I do in the SNMPTrap module above.

Alternatively, after your Step 4) but before Step 5), try:

Convert::ASN1::asn_dump($der);
Convert::ASN1::asn_hexdump($der);
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