... google for "gpg tutorial"..... then once you figure out how keys work, you can use something like this GnuPG example with with your keys.... search CPAN for other modules for GpG too.... some work better than others for different platforms

#!/usr/bin/perl
use warnings;
use strict;
use GnuPG;

# where you find your default keys, or you can specify an exact key
# get a tutorial, it's alot to explain

my $gpg = new GnuPG(homedir => '/home/z/.gnupg');

$gpg->encrypt(plaintext =>"Gnufile.txt", 
              output => "Gnufile.gpg",
              recipient =>"z\@z.net",
          armor=> 1,
          );
exit;
[download]

.... then you can mail off your secret file to anyone you want, and there are more details like clearsigning it, ...... it goes on and on ad infinitum in the spy vs. spy game :-)