This seems like a rather poorly defined problem. Let me try to reconstruct what you are trying to do:

• You have a number of clusters, for which you want to report total (or possibly average?) CPU usage %.
• Each cluster has a number of servers, whose names you need to keep track of so you can contact them for CPU info.

So one way to address this problem is to have a hash keyed by server name, and each hash entry's value is a reference to an array of values (server_name, CPU utilization).

Try something like this (untested) code to accumulate total CPU usage:

use strict;
use warnings;
my %server_hash = ( 
  'server1' => ['cluster1',0], 
  'server2' => ['cluster1',0], 
  'server3' => ['cluster2',0], 
  'server4' => ['cluster2',0] );

my %cluster_totals = ();
foreach my $this_server(keys %server_hash) {
  $server_hash{$this_server}->[1] = getCPUUtilization($this_server);
  $cluster_totals{$server_hash{$this_server}->[0]} += $server_hash{$th
+is_server}->[1];
}
foreach (keys %cluster_totals) {
  print "Cluster: $_ \t $cluster_totals{$_}\n";
}
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Granted, I'm using an extra hash where I probably don't need to, and this solution is off-the-cuff. But it might provide you with a starting point. The nice thing about a hash of array references is that it is extensible when you need to store yet another attribute of the server.