filehandle not returning lines

fraktalisman has asked for the wisdom of the Perl Monks concerning the following question:

The piece of code below is supposed to read 20 lines of an existing text file and set a mark ($marke) so the next time this piece of code gets executed, it would then skip the first $marke lines.

When $marke is still zero, everything goes as planned. Oddly, in the second run when $marke is 21, the file is not read line-by-line like it was in the first run, but the whole file goes into the $zeile string. Why?

The documentation and tutorials don't cover this problem. Is there something like line context (not exactly) that I could force my filehandle into?

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);
[download]

Update: corrected "line contest" to "line context". Problem is solved now, see below.

_{fraktalisman keeps rolling}

Comment on filehandle not returning lines Download Code

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Re: filehandle not returning lines by Hena (Friar) on Feb 18, 2005 at 10:57 UTC
Note that your adding to counter is after a next in the while loop. This probably means that your counter will not work properly. You probably want to put $counter++ first in while loop (or in continue block after while.	[reply]
Re^2: filehandle not returning lines by fraktalisman (Hermit) on Feb 18, 2005 at 11:03 UTC
Oooops! Bad mistake! And that's already the solution. No mysterious context bug or anything like that. Thanks a lot! Question answered. _{fraktalisman keeps rolling}	[reply]
Re: filehandle not returning lines by borisz (Canon) on Feb 18, 2005 at 10:48 UTC
if your whole file is read at once, it is most likely that some part of your program modify the `$/` var. `$/ The input record separator, newline by default.` Read the whole story with perldoc perlvar Boris	[reply]
Re^2: filehandle not returning lines by fraktalisman (Hermit) on Feb 18, 2005 at 10:53 UTC
Thanks for the idea. But I have just double checked the whole script if it accidentally messes with $/ but it doesn't. The same code is behaving as it should as long as the mark $marke==0, but this makes no sense to me. _{fraktalisman keeps rolling}	[reply]