C:\>type test.pl
use Data::Dumper;

my $a={ child1 => [ {child2 => [ { child3 => [ {child4 => [ 1 ] } ] } ] } ] }; 
print Dumper $a;
print Dumper $a->{child1};
print Dumper $a->{child1}{child2};
print Dumper $a->{child1}{child2}{child3};
print Dumper $a->{child1}{child2}{child3}{child4};

C:\>perl test.pl
$VAR1 = {
          'child1' => [
                        {
                          'child2' => [
                                        {
                                          'child3' => [
                                                        {
                                                          'child4' => [
                                                                        1
                                                                      ]
                                                        }
                                                      ]
                                        }
                                      ]
                        }
                      ]
        };
$VAR1 = [
          {
            'child2' => [
                          {
                            'child3' => [
                                          {
                                            'child4' => [
                                                          1
                                                        ]
                                          }
                                        ]
                          }
                        ]
          }
        ];
$VAR1 = undef;
$VAR1 = undef;
$VAR1 = undef;

C:\>

[root@devel3 root]# cat test.pl
use Data::Dumper;

my $a={ child1 => [ {child2 => [ { child3 => [ {child4 => [ 1 ] } ] } ] } ] }; 
print Dumper $a;
print Dumper $a->{child1};
print Dumper $a->{child1}{child2};
print Dumper $a->{child1}{child2}{child3};
print Dumper $a->{child1}{child2}{child3}{child4};
[root@devel3 root]# perl test.pl
$VAR1 = {
          'child1' => [
                        {
                          'child2' => [
                                        {
                                          'child3' => [
                                                        {
                                                          'child4' => [
                                                                        1
                                                                      ]
                                                        }
                                                      ]
                                        }
                                      ]
                        }
                      ]
        };
$VAR1 = [
          {
            'child2' => [
                          {
                            'child3' => [
                                          {
                                            'child4' => [
                                                          1
                                                        ]
                                          }
                                        ]
                          }
                        ]
          }
        ];
$VAR1 = undef;   # hangs for 5 seconds here
$VAR1 = undef;
$VAR1 = undef;
[root@devel3 root]#