#!c:/perl/bin/perl.exe
use strict;
use warnings;
use Data::Dumper;
use CGI qw/:all start_ul/;
my %navi = ( "Java" => {
                        "Switch" => ["Switch","switch.htm"],
                        "Bubble" => ["Bubblesort","Bubble.htm"]
                        },
             "Andere" => {
                        "Switch" => ["Switch","switch.htm"],
                        "Bubble" => ["Bubblesort","Bubble.htm"]
                         }
            );
my $navigation = '';
for my $key (sort keys %navi) {
  $navigation .= h4($key) . start_ul . "\n";
  for (sort keys %{$navi{$key}}) {
    $navigation .= a({-href=>$navi{$key}{$_}[1],-alt=>$navi{$key}{$_}[0]},$_) . "\n";
  }
  $navigation .= end_ul . "\n";
}
print $navigation;
_ _ END _ _
<h4>Andere</h4><ul>
<a href="Bubble.htm" alt="Bubblesort">Bubble</a>
<a href="switch.htm" alt="Switch">Switch</a>
</ul>
<h4>Java</h4><ul>
<a href="Bubble.htm" alt="Bubblesort">Bubble</a>
<a href="switch.htm" alt="Switch">Switch</a>
</ul>