@$arrayRef = ();
while (my $row = $sth->fetch()) {
   push @$arrayRef, $row;
}

##</code><code>##

@$arrayRef = ();
while (my $row = $sth->fetch()) {
   push @$arrayRef, [ @$row ];  # Make a copy.
}

##</code><code>##

@$arrayRef = @{ $dbh->selectall_arrayref($stmt_or_sth) };