You say you have the same keys and the same values in each hash, right? Meaning that doing:

 @keys=keys %hash1;
 @v1=@hash1{@keys};
 @v2=@hash2{@keys};
 @v3=@hash3{@keys};
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will result in @v1 etc. being each a permutation of the others?

If this is the case, I'd use the minimum number of swaps necessary to permute one hash into the other.

Keep in mind that differences are usually defined between two objects. What do you mean with 'least differing from other hashes'?

-- 
        dakkar - Mobilis in mobile