use Data::Dumper;
use Tie::IxHash;
tie %data, 'Tie::IxHash';

  do "File";

  $data{SomeMoreStuff}{SomeMoreData} = 'x';

  print Dumper \%data;

##</code><code>##

%data = (
SomeStuff => {
  SomeData => 'a',
  SomeMoreData =>'b',
  OtherData =>'c',
},
SomeMoreStuff => {
  SomeData =>'a',
  SomeMoreData => 'b',
  SomeExtraData => 'c',
  OtherData => 'd'
}
);

##</code><code>##

$VAR1 = {
          'SomeStuff' => {
                           'OtherData' => 'c',
                           'SomeMoreData' => 'b',
                           'SomeData' => 'a'
                         },
          'SomeMoreStuff' => {
                               'OtherData' => 'd',
                               'SomeMoreData' => 'x',
                               'SomeExtraData' => 'c',
                               'SomeData' => 'a'
                             }
        };

##</code><code>##

$VAR1 = {
          'SomeStuff' => {
                           'SomeData' => 'a'
                           'SomeMoreData' => 'b',
                           'OtherData' => 'c',
                         },
          'SomeMoreStuff' => {
                               'SomeData' => 'a'
                               'SomeMoreData' => 'x',
                               'SomeExtraData' => 'c',
                               'OtherData' => 'd',
                             }
        };