I don't think such a thing is possible. You can get away with writing them in C++ though.

On second thoughts, you might be able to write a bootstrapping .so which calls your perl code for you. But if you are good enough to do that, you would probably just code it directly in C/C++ yourself!

There are three PAM guides you should examine, if you haven't already, this page contains them all.

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Ash OS durbatulk, ash OS gimbatul,
Ash OS thrakatulk, agh burzum-ishi krimpatul!
Uzg-Microsoft-ishi amal fauthut burguuli.