Thanks, that did the trick.

use strict;
use warnings;
my $returncode;
$returncode = 0;

open (my $IN,"<c:/temp/logbook.log") || die "can not open datei: $!";

while(<$IN>){
  if( /error/i ){
     print;
     $returncode++;
  print "$returncode\n";
 }

 }

if ( $returncode == 0 ){
  my $file = '/temp/ok.txt';


   open FILE, '>', $file or die "Kann Datei $file nicht zum Schreiben 
+oeffnen: $!\n";

    print FILE "ok!\n";           

    close FILE;
}
close $IN;
[download]

Thanks
MH