push @{$H{$1}{$3}{head}}, $2;
    push @{$H{$1}{$3}{tail}}, grep{$_} split ':', $4;

##</code><code>##

foreach my $k1 (sort {$a <=> $b} keys %H) {
    print "$k1\n";
    foreach my $k2 (sort {$a <=> $b} keys %{$H{$k1}}) {
        print "$k2\n";
        my $tail = join ':', sort {$a <=> $b} @{$H{$k1}{$k2}{tail}};
        foreach my $head (sort {$a <=> $b} @{$H{$k1}{$k2}{head}}) {
            print "$head|$tail\n";
        }
    }
}