sub add {
    my ($self, $params, @query) = @_; 
    my ($callback, @ns);

    if (ref($params) eq 'HASH') {
        @query = @{ $params->{Query} } if exists $params->{Query};
        $callback = $params->{Callback};
        @ns = @{ $params->{Nameservers} } if exists $params->{Nameservers};
    }
    else {
        $callback = $params;
    }

    (...)
}