in the spirit of KISS, here is my easy solution :

my %clusters = 
(    
    cluster1 => ['h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'h7'],
    cluster2 => ['h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'h7'],
    # ...
);

foreach my $clust (sort keys %clusters) {
    foreach my $ind (0..5) {
        &process_1_6($clusters{$clust}[$ind]);
    }
    &process_7($clusters{$clust}[6]);
}
[download]

always more than one way to skin an amoebae
-- MZS