Here's a simple way to take the difference of sets. 
use Data::Dumper;
%one = ( 'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5, 'f' => 6,);
%two = ( 'a' => -1, 'e' => -2, 'i' => -3, 'o' => -4, 'u' => -5,);
print Dumper(\%one, \%two);

%tmp = %one;
delete @tmp{keys %two};
print Dumper(\%tmp);

%tmp = %two;
delete @tmp{keys %one};
print Dumper(\%tmp);

[download]
Running the above produces the following: 
$VAR1 = {
          'e' => 5,
          'c' => 3,
          'a' => 1,
          'b' => 2,
          'd' => 4,
          'f' => 6
        };
$VAR2 = {
          'e' => -2,
          'u' => -5,
          'a' => -1,
          'o' => -4,
          'i' => -3
        };
$VAR1 = {
          'c' => 3,
          'b' => 2,
          'd' => 4,
          'f' => 6
        };
$VAR1 = {
          'u' => -5,
          'i' => -3,
          'o' => -4
        };

[download]

In reply to Re^3: Reconcile one list against another by samwyse
in thread Reconcile one list against another by spartan

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