Digest::MD2 is on my CPAN mirror, however, the upload date was 4/28/2014, and the Changes file says this:
2014-04-28 Gisle Aas < email-removed >
Release 2.04
No change. I accidentally deleted the 2.03 dist from CPAN when trying
to clean up old Digest-MD5 dists.
So if your mirror didn't have Digest::MD2 on it, it's probably because it accidentally got deleted. But it's been uploaded again, and it's possible that by now the situation has resolved itself. If not, it will soon (or use a different mirror).
You can probably thank this blog entry.
The Digest::MD2 dependency comes through Crypt::RSA, of which Crypt::OpenPGP is a direct dependent. You may still have problems installing Crypt::OpenPGP though. I find on my system it fails a few tests, even if I use the "Alt::Crypt::RSA::BigInt" alternate dependency (which is sometimes useful as it removes the need for the difficult-to-install Pari math library).
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