use strict;
use warnings;

my ($k1, $k2, %foo, %bar);

%foo = (
         'a' => {
                  'x' => 1,
                  'y' => 3
                },
         'b' => {
                  'x' => 4,
                  'y' => 4
                }
       );
%bar = (
         'a' => {
                  'x' => 1,
                  'y' => 2
                },
         'b' => {
                  'x' => 3,
                  'y' => 4
                }
       );
for $k1 (sort keys %foo) {
    for $k2 (sort keys %{$foo{$k1}}) {
        print "\$foo{$k1}{$k2} eq \$bar{$k1}{$k2} with value $foo{$k1}{$k2}\n"
            if $foo{$k1}{$k2} eq $bar{$k1}{$k2};
    }
}