foreach my $key (keys %pssn) {
   if (not exists $assn{$key}) {
      push(@array, $key);
   }
}

foreach my $key (keys %assn) {
   if (not exists $pssn{$key}) {
      push(@array, $key);
   }
}

my %assn_vals = map { $_ => 1 } values %assn;
my %pssn_vals = map { $_ => 1 } values %pssn;

foreach my $val (keys %assn_vals) {
   if (not exists $pssn_vals{$val}) {
      push(@array, $val);
   }
}

foreach my $val (keys %pssn_vals) {
   if (not exists $assn_vals{$val}) {
      push(@array, $val);
   }
}