Solution to the task # 2.

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diff --git a/challenge-056/wanderdoc/perl/ch-2.pl b/challenge-056/wanderdoc/perl/ch-2.pl
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+#!perl
+use strict;
+use warnings FATAL => qw(all);
+
+
+
+=prompt
+You are given a binary tree and a sum, write a script to find if the tree has a path such that adding up all the values along the path equals the given sum. Only complete paths (from root to leaf node) may be considered for a sum.
+
+Example:
+
+Given the below binary tree and sum = 22,
+
+          5
+         / \
+        4   8
+       /   / \
+      11  13  4
+     /  \      \
+    7    2      1
+
+For the given binary tree, the partial path sum 5 → 4 → 11 = 20 is not valid.
+The script should return the path 5 → 4 → 11 → 2 which sum is 22.
+
+=cut
+
+use Tree::DAG_Node;
+use List::Util qw(sum);
+
+my $SUM = shift || 22;
+
+my $root = Tree::DAG_Node -> new({name => 5});
+my $l_node = $root->new_daughter({name => 4});
+my $r_node = $root->new_daughter({name => 8});
+
+my $n11 = $l_node->new_daughter({name => 11});
+my $n7 = $n11->new_daughter({name => 7});
+my $n2 = $n11->new_daughter({name => 2});
+
+my $n13 = $r_node->new_daughter({name => 13});
+my $n4 = $r_node->new_daughter({name => 4});
+my $n1 = $n4->new_daughter({name => 1});
+
+
+print map("$_\n", @{$root->draw_ascii_tree});
+
+my @paths = $root->leaves_under();
+my @output;
+
+for my $path ( @paths )
+{
+     $path->walk_down({
+        callback => sub {
+                my $node = shift;
+                my @this_sum;
+                unshift @this_sum, $node->name; 
+                my @anc = $node->ancestors();
+
+                for my $an ( @anc ) 
+                { 
+                    unshift @this_sum, $an->name; 
+                }
+                push @output, [@this_sum];
+        },
+    })
+}
+
+# use Data::Dump; dd @output;
+@output = grep $SUM == sum(@$_), @output;
+print join("->", @$_), $/ for @output;
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