HR   while (my $ref = $sth->fetchrow_hashref) {
         # use $ref->{c_base} and $ref->{base}

A    while (my ($c_base, $base) = $sth->fetchrow_array) {
         # use $c_base and $base

AR   while (my $ref = $sth->fetchrow_arrayref) {
         # use $ref->[0] and $ref->[1]

DAR  while (my $ref = DBI::st::fetchrow_arrayref ($sth)) {
         # use $ref->[0] and $ref->[1]

BC   $sth->bind_columns (\my ($c_base, \$base));
     while ($sth->fetch) {
         # use $c_base and $base

DBC  $sth->bind_columns (\my ($c_base, \$base));
     while (DBI::st::fetchrow_arrayref ($sth)) {
         # use $c_base and $base