use warnings;
use strict;

my $infile = 'exportiert.csv';
open (my $infile_fh, '<', $infile) or die "Kann $infile nicht lesen\n";

my $outfile = 'kurz.csv';
open (my $outfile_fh, '>', $outfile) or die "Kann $outfile nicht schreiben\n";

while (my $line = <$infile_fh>) {
    my @fields = split /;/, $line;
    for my $field (@fields) {
        if (length($field) > 30) {
            $field = substr($field, 0, 30);
        }
    }
    print $outfile_fh join(';', @fields);
}