open my $fh, "<:encoding(utf8)", "output.csv" or die "output.csv: $!";
my $csv = Text::CSV->new({binary=>1, auto_diag=>2, eol=>$/,
    always_quote=>1 });
$csv->print($fh, (select, ["sku", @columns]));
for my $sku (sort keys %$itms) {
    $csv->print($fh, (select, [$sku, map { $itms->{$sku}{$_} } @columns ]));
}