This is how I was able to do it. But it might not be a generalized solution 

$seen{$chr1}++;
    $seen{$chr2}++;
    if (($seen{$chr1}>1)||($seen{$chr2}>1)){
        next;
    }    
    else{
          $hash_chr{$chr1}=$chr2;
          }

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In reply to Re^2: hash with both values and keys unique to each other by perlkhan77
in thread hash with both values and keys unique to each other by perlkhan77

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