push @{ $data->{Things}->{Thing} },
    {
    'Item' => $var1,
    'Number' => $var2,
    'Details' => {
            'Detail' => {
                    'Color' => $var3
                        }
             },
    'AdditionalInfo' => {
        'Info' => $var4,
        'Stuff' => $var5,
        'MoreDetails' => {
                'ExtraColor' => $var6
                 }
        }
    };

##</code><code>##

$struc={
        'Item' => $var1,
        'Number' => $var2,
        'Details' => {
                      'Detail' => {
                                   'Color' => $var3
                                  }
                     }
       }
$struc->{AdditionalInfo}={
                          'Info' => $var4,
                          'Stuff' => $var5,
                          'MoreDetails' => {
                                            'ExtraColor' => $var6
                                           }
                         };
push @{ $data->{Things}->{Thing} },$struc;