Now I have checked this Data structure, and everything seems to be saved properly and nothing overwritten etc.

You don't say how you did the checking but, if you haven't found it already, Data::Dumper is a very useful tool when you need to inspect your data structures. This

use strict;
use warnings;

use Data::Dumper;

my %hash = (
   this => [ 1, 2, 4, 8 ],
   that => { the => q{other} },
   );

print Data::Dumper->Dumpxs( [ \ %hash ], [ qw{ *hash } ] );
[download]

produces this

%hash = (
          'that' => {
                      'the' => 'other'
                    },
          'this' => [
                      1,
                      2,
                      4,
                      8
                    ]
        );
[download]

I hope this is helpful.