for my $key_primary (keys %internal_hash_ref) {

  print qq{primary key: *$key_primary*\n};

  for my $key_secondary (keys 
%{$internal_hash_ref{$key_primary}}){

    print qq{\tsecondary key: *$key_secondary*\n};
    print qq{\t\t*@{$internal_hash_ref{$key_primary}{$key_secondary}}*\n};

  }

}