Not sure what you mean by "access each element", since the elements seem to be a variety of different structures, but here's how to get into the structure a couple levels. For everyone else's benefit, I added something into that hole at the bottom and then ran this through Data::Dumper first and eliminated a bunch of the whitespace at the left side to clean it up.

use strict;
use warnings;

my $nested = {

'Systemreaction' => [
                      {
                        'Data' => 'x'
                      },
                      {
                        'Data' => 'x'
                      }
                    ],
'Service' => [
               {
                 'Customers' => [
                                  {
                                    'SW' => [
                                              {
                                                'Path' => '/work/servi
+ce.xml',
                                                'Service' => 'ASOC'
                                              }
                                            ]
                                  }
                                ],
                 'Id' => 'SKRM',
                 'Name' => ' Control unit',
                 'Suppliers' => [
                                  {
                                    'SW' => [
                                              {
                                                'Path' => '/work/servi
+ce.xml',
                                                'Service' => 'b7a'
                                              },
                                              {
                                                'Path' => '/work/servi
+ce1.xml',
                                                'Service' => 'b7b'
                                              },
                                              {
                                                'Path' => '/work/servi
+ce2.xml',
                                                'Service' => 'b5'
                                              }
                                            ]
                                  }
                                ],
                 'Des' => 'Control the current through the pipe'
               },
               {
                 'Customers' => [
                                  {
                                    'SW' => [
                                              {
                                                'Path' => '/work/servi
+ce.xml',
                                                'Service' => 'SDCR'
                                              }
                                            ]
                                  }
                                ],
                 'Id' => 'ADTM',
                 'Name' => ' Motor Drivers and Diognostics',
                 'Suppliers' => [
                                  {
                                    'HW' => [
                                              {
                                                'Type' => 'W',
                                                'Path' => '/work/hardw
+are.xml',
                                                'Nr' => '18',
                                                'Service' => '1'
                                              },
                                              {
                                                'Type' => 'B',
                                                'Path' => '/work/hardw
+are.xml',
                                                'Nr' => '7',
                                                'Service' => '1'
                                              },
                                              {
                                                'Type' => 'k',
                                                'Path' => '/work/hardw
+are.xml',
                                                'Nr' => '1',
                                                'Service' => '1'
                                              }
                                            ]
                                  }
                                ],
                 'Des' => 'It delivers actual motor speed'
               }
             ]
};

for my $service (@{$nested->{'Service'}}) {
    print "$service->{'Name'}\n";
}
for my $system (@{$nested->{'Systemreaction'}}) {
    print "$system->{'Data'}\n";
}
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