One function -> One page
sub get_email_address {
my ($app) = @_;
$app->build_page('enter_email_address.tmpl', $param);
}
sub validate_email_address {
my ($app) = @_;
my $email = $app->{query}->param('email');
if ($email and Email::Valid->address($email)) {
send_letter();
}
else {
$app->get_email_address;
}