You pull your values and immediately clear the array

my %row =();
$sth->bind_columns(map {\$row{$_}} @Rcols);
while (@values=$sth->fetchrow_arrayref) {
    @values = '';
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Also note, your bind_columns statement can be simplified a little by taking the reference of a hash slice

$sth->bind_columns(\@row{@Rcols});
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Update: Nevermind, appears you figured it out above