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diff --git a/challenge-057/luca-ferrari/raku/ch-1.p6 b/challenge-057/luca-ferrari/raku/ch-1.p6
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+#!env raku
+
+# Perl Weekly Challenge 57
+# see <https://perlweeklychallenge.org/blog/perl-weekly-challenge-057/>
+#
+# Task 1
+
+class Node {
+    has Int  $.value;
+    has Node $.left  is rw;
+    has Node $.right is rw;
+
+
+}
+
+
+sub switch( Node $current-node is rw ) {
+    return if ! $current-node
+        && ! $current-node.left
+        && ! $current-node.right;
+
+    my ( $left, $right ) = ( $current-node.left, $current-node.right );
+    $current-node.left  = $right;
+    $current-node.right = $left;
+
+    switch( $current-node.left )  if $current-node.left;
+    switch( $current-node.right ) if $current-node.right;
+}
+
+
+
+sub print( $left, $right, $height ) {
+    my $message = "%s %s %s".sprintf: "  " x $height,
+        $left ?? $left.value !! " ",
+        $right ?? $right.value !! " ";
+
+    $message ~= print( $left.left, $left.right, $height - 1 ) if $left;
+    $message ~= print( $right.left, $right.right, $height- 1 ) if $right;
+    return $message;
+}
+
+sub MAIN() {
+
+    my Node $root     = Node.new( :value( 1 ) );
+    $root.left        = Node.new( :value( 2 ) );
+    $root.right       = Node.new( :value( 3 ) );
+    $root.left.left   = Node.new( :value( 4 ) );
+    $root.left.right  = Node.new( :value( 5 ) );
+    $root.right.left  = Node.new( :value( 6 ) );
+    $root.right.right = Node.new( :value( 7 ) );
+
+    switch( $root );
+    #    put $root.Str;
+    say print $root, Nil, 5;
+
+}