I guess you meant the inner while loop?

while (my $data = $sth->fetchrow_hashref()) {
    # %$data is now a hash.
    # keys are the column's names
    # values are the column's values
    while (my($k, $v)= each %$data) {
        # Now I loop over each column-value pair
        push( @{$results{$k}}, $v );
        # pushing into the results' hashes all the values.
        # So $result{'canning'} is a reference to an array
        # for all the canning-values etc.pp.
    }
}
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