sub write_columns {
    my ($fh, $columns) = @_;
    if (defined($columns->{$fields[0]})) {
        $csv->print($fh, [ @{$columns}{ @fields } ]);
    }
}

open(my $fh, '>', $qfn)
    or die("Can't create output file \"$qfn\": $!\n");

write_columns($fh, $columns);