GnuPG is a perl module that interface with the Gnu Privacy Guard using the coprocess hooks provided by gpg. The communication mechanism uses is shared memory and a status file descriptor.
The module tries it best to map the rather interactive interface of gpg to a more programmatic API.
Also the modules now offers a tied file handle interface to encryption and decryption making a lot more easy to use.
This module doesn't yet provides an interface to the key manipulation facilities of gpg.
It doesn't also provides the memory protection offered by gpg when manipulating user passphrase.
There are also several options (like cipher selections) that aren't available from the perl API.