my $filename2 = 'beispiel.csv';
if (open(my $fh2, '+<:encoding(UTF-8)', $filename2)) {

 while (my $row2 = <$fh2>) {

my $laenge=length($row2);

                         if ($laenge ==  $globla)
                         {
 
                        for my $stellen (@stellen)
                          {
                           substr $row, $stellen,1,';';
                          }


                         print $fh2 $row2;

                         }
 }
} else {
  warn "Could not open file '$filename2' $!";
}