fetchall_arrayref returns zero if the query failed

my $result_array  = $sth->fetchall_arrayref;

if (!$result_array) {
   print "query failed!!\n";
}
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If no rows are found (the query is successful, but no rows are returned) fetchall_arrayref returns a reference to an empty array.

my $result_array = $sth->fetchall_arrayref;

if ($result_array) {
    print "success\n";
    if (@$result_array) {
        print "found rows @$result_array\n";
    }
    else {
        print "no rows returned\n";
    }
}
else {
    print "query failed!!\n";
}
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