while( <LOG> ) {
   next unless m[ACK (...)]i;
   async( \&checkMAC, $1 )->detach;
}

##</code><code>##

sub checkMAC{
    my $mac = shift;
    
    ## If this is a known MAC & it has previously authorised successfully
    if( exists $clients{ $mac } and $clients{ $mac } ) {
        
        ## Check with the activity monitor to see if it has fallen inactive 
        my $active = get "http://activityServer/check.pl?mac=$mac";
        
        ## If is has never fallen inactive, it is known, authorised, and active
        ## and there is nothing to do
        return if $active;
        
        ## Not sure that this is really necessary, 
        ## but it might save a little resource.
        lock %clients;
        delete $clients{ $mac };
    }
    
    ## Otherwise, check http & Auth and modify status (or add) in %clients
    my $httpRes = get ...;
    my $authRes = get ...;

    lock %clients;
    $clients{ $mac } = $httpRes && $authRes ? 1 : 0;

    return.
}