use Crypt::OpenPGP;
...
my $pgp = Crypt::OpenPGP->new;
my($userid,$sigobj) = $pgp->verify(
        Signature       =>      $mailbody,
        Data            =>      $mailbody,
);
unless(defined $userid){
        done(1,"Could not verify signature.");
}
printf("KeyID: 0x%x\nUserID:%s\n",$sigobj->key_id, $userid);