use strict;
use warnings;

my @tree = ( 'ng1',
						 [ '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' ],
						 'ng2', 
						 [ 'ng2_1', [ 'ng2_1_u1', 'ng2_1_u2', 'ng2_1_u3' ],
							 'ng2_2', 'ng2_3', 'ng2_4' ],
						 'ng3',
						 [ 'ng3_1', 'ng3_2', 'ng3_3', 'ng3_4' ],
		);

sub findElementPosition{
		my ($tree,$position,$parent,$needle) = @_;
		my $previous;
		my $pos = 0;
		for my $treeElement (@{$tree}){
				if (ref $treeElement eq "ARRAY"){
						findElementPosition($treeElement,[@$position,$pos],$previous,$needle);
				}	else {
						if ($treeElement eq $needle){
								print "[$_]" for @$position[0..@$position-2];
								print "[",$position->[-1]-1,"] $parent \n";
						}
						$previous = $treeElement;
				}
				$pos++;
		}
}

my @position;

findElementPosition( \@tree, \@position, "", "ng1_1_1_u3" );
findElementPosition( \@tree, \@position, "", "ng3_1" );