sub recv_data{
    if(read_some_data){
        return($stuff1, $stuff2);
    } else {
        return;
    }
}

##</code><code>##

while(($x, $y) = recv_data){
    ...
}

##</code><code>##

while(1){
    my($x, $y) = recv_data;
    last unless defined $x;
    ...
}