perl => sub {
            require Syntax::Highlight::Perl;
            my ($data) = @_;
            my $hl = Syntax::Highlight::Perl->new;
            $hl->define_substitution(
                '<' => '&lt;',
                '>' => '&gt;',
                '&' => '&amp;',
                "\t" => '&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;',
                ' ' => '&nbsp;',
            );
            $hl->set_format( $_ => [ "<span class=$_>", "</span>" ] )
                for qw/Comment Directive Label Quote String Subroutine Variable
                       Keyword Builtin Operator Package Number CodeTerm Symbol
                       DATA/;
            return '<link rel=stylesheet href="/perl.css"><pre>' .
                   $hl->format_string($data) . '</pre>';
        },