sub encode {
    state $lookup = {
        '"' => '"',
        '&' => '&',
        '<' => '&lt;',
        '>' => '&gt;',
        map((chr($_), "&#$_;"), (0..31)),
    };
    state $re = do { my $tmp = join('', keys %$lookup); qr/([$tmp])/ };
    
    my ($text) = @_;
    return '' unless defined $text;
    $text =~ s/$re/$lookup->{$1}/g;
    return $text;
}