Please see if this subroutine makes sense for your problem:

sub foo_non_subsets {
  my ($h1, $h2) = @_;
  my %r;
  for my $c (List::Compare->new([keys %$h1], [keys %$h2])) {
    $r{$_} = $h1->{$_} for $c->get_Lonly;
    for ($c->get_union) {
      unless (List::Compare->new($h1->{$_}, $h2->{$_})->is_LsubsetR) {
        $r{$_} = $h1->{$_};
      }
    }
  }
  %r
}
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