HList copy constructor:
   DoubleNode clone
   DoubleNode clone
   IntNode clone
   StringNode clone
   IntNode clone
   IntNode clone
   StringNode clone
   IntNode clone


 Entering foo():

   StringNode destructor
   HNode destructor
   HNode destructor


 Exiting foo():

HList copy constructor:
   DoubleNode clone
   DoubleNode clone
   IntNode clone
   StringNode clone
   IntNode clone
   IntNode clone
   StringNode clone
   IntNode clone
   DoubleNode clone
   DoubleNode clone
   IntNode clone
   StringNode clone
   IntNode clone
   IntNode clone
   StringNode clone
   IntNode clone
HList Destructor:
   HNode destructor
   HNode destructor
   HNode destructor
   StringNode destructor
   HNode destructor
   HNode destructor
   HNode destructor
   StringNode destructor
   HNode destructor
   HNode destructor
   HNode destructor
HList Destructor:
   HNode destructor
   HNode destructor
   HNode destructor
   StringNode destructor
   HNode destructor
   HNode destructor
   HNode destructor
   StringNode destructor
   HNode destructor
   HNode destructor
   HNode destructor
HList Destructor:
   HNode destructor
   HNode destructor
   HNode destructor
   StringNode destructor
   HNode destructor
   HNode destructor
   HNode destructor
   StringNode destructor
   HNode destructor
   HNode destructor
   HNode destructor
HList Destructor:
   HNode destructor
   HNode destructor
   HNode destructor
   StringNode destructor
   HNode destructor
   HNode destructor
   HNode destructor
   StringNode destructor
   HNode destructor
   HNode destructor
   HNode destructor
In main(),  L1 = 2.78 3.14158 6 "Hello" 7 8 "World" 9 

In foo(), L3 = 2.78 3.14158 6 "Hello" 17 8 "New York" 9 

In main(),  L1 = 2.78 3.14158 6 "Hello" 7 8 "World" 9 

In main(), L2 = 2.78 3.14158 6 "Hello" 17 8 "New York" 9