Task

Demonstrate a language's methods of:

   variable declaration
   initialization
   assignment
   datatypes
   scope 
   referencing,     and 
   other variable related facilities


foobar = 15
 
f x = x + foobar
  where foobar = 15
 
f x = let foobar = 15
      in  x + foobar
 
f x = do
    let foobar = 15
    return $ x + foobar