Crypt::OpenPGP::Buffer is a binary in/out buffer.
my $buf = Crypt::OpenPGP::Buffer->new;
my $m = $buf->get_mp_int;
Crypt::OpenPGP::Buffer subclasses the Data::Buffer class to provide binary in/out buffer capabilities for Crypt::OpenPGP. In addition to the standard Data::Buffer methods, this class adds methods to get and put multiple-precision integers (Math::Pari objects).
A PGP multiple precision integer is stored in two pieces: a two-octet scalar representing the length of the integer in bits, followed by a string of octets that is a serialized representation of the integer.