perl -le '
  use strict;
  use warnings;
  use Data::Dumper;
  my @arr = ("ng1", ["ng1_1", "ng1_2", "ng1_2"]);
  my @tree;
  $tree[0] = $arr[0];
  $tree[1] = $arr[1];
  $tree[1] = '2';
  print Dumper @arr;
'