You might consider switching to Crypt::OpenPGP instead of GPG.pm. It seems to work fine.

#!/usr/bin/perl -w

use strict;
use CGI::Carp qw(fatalsToBrowser);  #show us the errors in the browser
use Crypt::OpenPGP;                    

my $gpg = Crypt::OpenPGP->new;

my $encrypted = $gpg->encrypt(
         Data => "Testing GPG",
         KeyID => $ARGV[0],
         Armour => 1,
   ) || die $gpg->errstr;

print <<"_END_";
Content-type: text/plain

Encrypted: -> $encrypted <-
_END_
[download]

helphand@helphand:~> perl gpg.pl helphand@pacbell.net
Content-type: text/plain

Encrypted: -> -----BEGIN PGP MESSAGE-----
Version: Crypt::OpenPGP 1.03

hQEOA3chMi/0iuq/EAP/ayJ2CjLe0svhfwI3w39/1ZjzoqX9hmWT8anhaMRgXrPo
kcw6o0W2MsuxELezZkHNIN7zJwq/JDA7fp58xy6bAaYpNxEhH8W4tmzHZJq777kt
kVQXVIi5c7g8SFc9T9u6CZHAh494Z2DZMILyCIh2h098SeXefrBjRXyd2nQu6MAE
AOYfzSetZM8OROHatTGdXCS7mqId5OdleMCrPRbjRhICiN3A2hyNVOwJFDnSvPbv
tc1HzLXkpC5oiAYhTqejXF2S6zG0BEj8RDyodhwP9lIr6O6UGLLDkDiU7gjY+cLt
9hsdLgGsiQz8gZg8Y6tYR20c+pMSP/0fbYlXh7qcJgxOpB3lonRzbWjJ0VC+MYG5
1WIARDzLZo83ncscqnSoLA==
=9lvU
-----END PGP MESSAGE-----
 <-
[download]

Scott