my $data = shift;
my @clusters;
my $elementsAlreadyUsed = [];
while (my $nextCluster = findNextCluster($data, $elementsAlreadyUsed))
{
  push @clusters, nextCluster;
}

# Loop over each cluster
for my $clusterID (0.. $#clusters)
{
  print "Cluster $clusterID (#". ($clusterID +1) . ")\n";  

  # Print the elements contained in the cluster
  print "\tContains element(s): ". (join ', ', @{$clusters[$clusterID]}) . "\n";
}

sub findNextCluster
{
  my $data = shift;
  my $elementsUsed = shift;

  # Pick first unused element to start from.
    # Return undef if all elements are used.
  # DFS or BFS over data connected to the start element;

  return BFSResultArrayRef($data, $startElement);
}