I don't know what system you're on, but the pari library is known to be difficult to get installed correctly on many systems (Debian, for example). And Crypt::OpenPGP depends on Crypt::RSA, which depends on Math::Pari, somewhere in its dependency chain.

Alt::Crypt::RSA::BigInt was designed by Dana Jacobsen to install and masquerade in place of Crypt::RSA. Just installing the "Alt" version of the module changes the dependency automatically. The "BigInt" in the module's title is a clue that it, internally, uses Math::BigInt, which can use gmp for fast big integer support. The gmp toolchain installs more reliably on a larger percentage of systems than pari. I wish I had the development conversation threads relating to this still handy... probably somewhere in my Gmail. :)

So, to summarize, in a test environment, install libgmp, Alt::Crypt::RSA::BigInt, and then Crypt::OpenPGP. Then run your code and see if you still get a silent crash. Hopefully not. ;)