use Captcha::reCAPTCHA;

    my $c = Captcha::reCAPTCHA->new;

    # Output form
    print $c->get_html( 'your public key here' );

# Verify submission
    my $result = $c->check_answer(
        'your private key here', $ENV{'REMOTE_ADDR'},
        $challenge, $response
    );

    if ( $result->{is_valid} ) {
        print "Yes!";
    }
    else {
        # Error
        $error = $result->{error};
    }

sub registration_page {
  my ($session, $q) = @_;
  
  my $c = Captcha::reCAPTCHA->new;
  push @tpl_data, (
                   captcha      => $c->get_html($conf{captcha_pubkey}),
                   pagetitle    => 'New User Registration',
                  );

  # Bail out if we're displaying the blank form instead of processing a
  # submission
  return 'register.tpl' unless $q->param('registerbtn');

  # Check captcha
  my $result = $c->check_answer($conf{captcha_privkey}, $ENV{'REMOTE_ADDR'},
                                $q->param('recaptcha_challenge_field'),
                                $q->param('recaptcha_response_field'));
  unless ($result->{is_valid}) {
    push @message_loop, { errstr => get_message('captcha_failed') };
    return 'register.tpl';
  }

  # Verify all required data present and save to database if so

  push @message_loop, { msgstr => get_message('register_ok') };
  return 'main.tpl';
}