#!/usr/bin/perl

use strict;
use warnings;

my @name = ("heinz", "karl", "Peter", "Anne", "heinz", "Anne");
my @geb = ("20101920", "23011929", "02121915", "06041966","20101920", "07071977");

my %all; # Verschachtelter Hash für den ganzen Datenbestand

for my $i (0..$#name) {
    $all{$name[$i]}->{$geb[$i]} .= "Rechnung Nr. $i ";
}

for my $nam (sort keys %all) {
    for my $geb (sort keys %{$all{$nam}}) {
        print "$nam, $geb: $all{$nam}->{$geb}\n";
    }
}