I have a pairwise distances between objects stored as double hash (the keys 1 and 2 are stored in alphabetical order): 

$distances{$key1}{$key2} = $value;

[download]

for example: 

obj1 obj2 => 0.95
obj2 obj3 => 0.76
obj1 obj4 => 0.80
...

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I have initiated an array of hashes, so that the object names are keys and they point to the name of subset I want to group them into (five subsets in total), so that: 

@subsets = (
{
    obj1  => "C1",
    obj2  => "C2",
    obj3  => "C3",
    obj4  => "C4",
    obj5  => "C5",
}
);

[download]

I also store already used object names in a separate hash: 

%used = (
{
    obj1  => "C1",
    obj2  => "C2",
    obj3  => "C3",
    obj4  => "C4",
    obj5  => "C5",
}
);

[download]

Now I want to look up the highest pairwise distance for each object in $subsets[0] (value from %distances), and append the 'partner's' key to the $subsets[ 1], with the same value (C1-C5) (For instance, if the obj1, which points to C1 has the highest pairwise distance with obj6, then I want to store obj6 as key and C1 as value). Also, I need to add each new object to the %used, as to make sure if the pair has not been used before. Alternatively, I could remove the used up pairs from %distances. 

for ($i = 0; $i < 50; $i++) { #loop over array of hashes (each subset 
+will have 50 keys)
    foreach my $key (keys $subsets[$i]) { #5 keys at each level
        my $max = 0;
        my @max;
        for my $key1 (keys %distances) {
            if $key !exists (keys %used) {
                $max = max (values %{$distances{$key1}});
                push @max, $max;
                # somehow retrieve the 2nd key
            }
        }
        my $maxmax = max @max;
        # $subsets[$i+1]{2nd_key_with_max_val} = "e.g. C1"
        # push %used with key and value
        @max = [];
    }
}

[download]

...but I clearly have problems making it work. Any ideas?

In reply to Separating hashed data into subsets by monkini

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