my $mtime = 0;
my $latestfile = "";
find(\&wanted, "/var/bin/testverzeichnis/Projekte/Projektenummern/12/1234");
print "$latestfile\n";

sub wanted {
    my $name = $File::Find::name;
    if (-f $name) {
        my @stats = stat($name);
        if ($stats[9] > $mtime) {
            $mtime = $stats[9];
            $latestfile = $name;
        }
    }
}