bla.pl

#!/usr/bin/env perl
use strict;
use warnings;
use Storable qw/dclone/;
use Data::Dumper;

my $a = {
          '%h_outside' => {
                            'a' => 1,
                            'b' => 2
                          },
          '@a_inside' => [
                           'x',
                           'y',
                           3
                         ],
          '$s_inside' => 42,
          '$r_inside' => undef,
          '$r2_outside' => undef,
          '$s_outside' => 42,
          '%h_inside' => {
                           'a' => 1,
                           'b' => 2
                         },
          '$r2_inside' => $a->{'$r_inside'},
          '@a_outside' => [
                            'x',
                            'y',
                            3
                          ],
          '$r_outside' => $a->{'$s_outside'},
        };

my $b = {
          '%h_outside' => {
                            'a' => 1,
                            'b' => 2
                          },
          '$r2_outside' => undef,
          '$s_outside' => 42,
          '@a_outside' => [
                            'x',
                            'y',
                            3
                          ],
          '$r_outside' => $a->{'$s_outside'},
        };


#######################
# computing complement
#######################

my $b_c = dclone($a) ; # completement of $b with respect to $a
delete $b_c->{$_} for keys %{$b};

print Dumper $b_c;