There is (or was) a tutorial on pack and unpack that included examples for encode/decoding files in Intel Hex format. The order of the fields is different and the record introducer is different. but I think the checksum is the same. Anyway, that should be a good start.

I have used those examples in my own projects. (I will try to post my Perl code, tonight or tomorrow.)

I have also been intending to make S-rec versions, but one of the (proprietary) tool suites I use for work includes a tool for converting so I've never had an urgent enough need to handle S-recs directly in Perl.