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);