open(TODO,"<datei.txt") or &fehler;
while ($zeile=<TODO>) {
 print "$counter $zeile\n"; # debugging: what is actually read?
 chomp $zeile;
 next if ($counter<$marke);
 if ($counter>($marke+20)) { $stilltodo=1; last; }
 push (@liste,$zeile);
 $counter++;
}
close(TODO);