{
    my ($lookup, $re);

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