Basically, I have an array called @host_array that contains information about the hosts that I want to see whether they are alive or dead. I need to check their current status against their old status and send an alert if something changes. Unfortunately, I can't seem to get the reference right. That means that when I update a value in the $task variable within sub 'pinger', it doesn't actually update the original array; just its local version of the data.

I want to pass a reference to the entire array to run_threaded and then a reference to a slice of that array from run_threaded to pinger.

populateHosts(1);

while (1) {
    run_threaded(10,\&pinger,\@host_array);
}

sub run_threaded {
    my ($threads,$func_to_thread, $hosts) = @_;
    my (%threads);
    my $n = 0;
    my $debug = 1;
    
    my $m = $threads-1 > $#{$hosts} ? $#{$hosts} : $threads-1;
    while (1) {
        last if $n >= $#{$hosts}+1;
        
        foreach my $host (@$hosts[$n..$m]) {
            #Still a reference here!  I can change the value of $host[
+x] and it will stick.
            $threads{$host} = new threads $func_to_thread, $host;
            
        }
        map { 
            $threads{$_}->join if $threads{$_}; 
        } 
        @{$hosts}[$n..$m];
        # work out the next range of instances to work on
        $n = $m == 0 ? 1 : $m+1;
        $m = $n+$threads-1 < $#{$hosts} ? $n+$threads-1 : $#{$hosts};
        
    }
    
}

sub pinger{
    $task = shift;
    
    # Create pinger
    $p = Net::Ping->new("tcp");
    $p->port_number($task->[4]);
    
    
    if( $p->ping($task->[3], 6) ) {
        print "  PASS: @$task[2] ";
        $task->[5] = 1;
        #I want to update @host_array, but it's not a reference!
    } else {
        print "  FAIL: @$task[2] ";
        $task->[5] = 0;
        #I want to update @host_array, but it's not a reference!
    }
    $task->[2] .= "-2";
    $p->close();
}

sub populateHosts {
    ($init) = @_;
    # DEFINE A MySQL QUERY
    $query = "SELECT * FROM `sites`";

    # EXECUTE THE QUERY
    $db->query($query);
    my $set = $db->create_record_iterator;

    $i=0;
    while (my $rec = $set->each) {
        $host_array[$i][0] = $i;
        $host_array[$i][1] = $rec->[0];
        $host_array[$i][2] = $rec->[1];
        $host_array[$i][3] = $rec->[2];
        $host_array[$i][4] = $rec->[3];
        if ($init) {
            $host_array[$i][5] = $rec->[4];
            $host_array[$i][8] = $rec->[5];
            $host_array[$i][6] = 1;
            $host_array[$i][7] = time;
        }
        $i++;
    }
}
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There are some lines that I omitted for brevity, but the function should still be similar. Thanks!

By the way, the great thread function 'run_threaded' came from http://greg-techblog.blogspot.com/2009/06/threading-in-perl.html