$VAR1 = 'ng1';
$VAR2 = [
          'ng1_1',
          [
            'ng1_1_1',
            [
              'ng1_1_1_u1',
              'ng1_1_1_u2',
              'ng1_1_1_u3'
            ],
            'ng1_1_2',
            'ng1_1_3',
            'ng1_1_4'
          ],
          'ng1_2',
          'ng1_3',
          'ng1_4'
        ];
$VAR3 = 'ng2';
$VAR4 = [
          'ng2_1',
          [
            'ng2_1_u1',
            'ng2_1_u2',
            'ng2_1_u3'
          ],
          'ng2_2',
          'ng2_3',
          'ng2_4'
        ];
$VAR5 = 'ng3';
$VAR6 = [
          'ng3_1',
          'ng3_2',
          'ng3_3',
          'ng3_4'
        ];

##</code><code>##

 [0]            ng1
  [1][0]          ng1_1
   [1][1][0]        ng1_1_1
    [1][1][1][0]     ng1_1_1_u1
    [1][1][1][1]     ng1_1_1_u2
    [1][1][1][2]     ng1_1_1_u3
   [1][1][2]        ng1_1_2
   [1][1][3]        ng1_1_3
   [1][1][4]        ng1_1_4
  [1][2]          ng1_2
  [1][3]          ng1_3
  [1][4]          ng1_4
 [2]            ng2
  [3][0]          ng2_1
   [3][1][0]       ng2_1_u1
   [3][1][1]       ng2_1_u2
   [3][1][2]       ng2_1_u3
  [3][2]          ng2_2
  [3][3]          ng2_3
  [3][4]          ng2_4
 [4]            ng3
  [5][0]          ng3_1
  [5][1]          ng3_2
  [5][2]          ng3_3
  [5][3]          ng3_4

##</code><code>##

# &findElementPosition(\@tree,"ng1_1_1_u3");
#
sub findElementPosition{
  my ($tree,$needle) = @_;
  for my $treeElement (@{$tree}){
    if (ref $treeElement eq "ARRAY"){
	  push @position,0;
	  &findElementPosition($treeElement,$needle);
	  pop @position;
	  $position[-1]++;
    }
    else{
	  if ($treeElement eq $needle){
	    for (@position){ print "[$_]" }
		print " " . $treeElement . "\n";
	  }
      $position[-1]++;
    }
  }
}

##</code><code>##

[1][1][1][2] ng1_1_1_u3

##</code><code>##

pop @position;
$position[-1]--;