   defmacro case(condition, blocks)
 
   @doc """
-  Execute the given expressions and catch any error, exit
+  Evaluate the given expressions and catch any error, exit
   or throw that may have happened.
 
   ## Examples

        value -> value
      end

  In the example above, we compare `thing` with each given
  match clause and execute the first one that matches. If no
  clause matches, an error is raised.

  Since Elixir variables can be assigned more than once, variables

  end

  @doc """
  Evaluates and returns the expression unless clause evaluates to true.
  Returns nil otherwise.
  See also `if`.

  ## Examples

      iex> unless(1, "Hello")
      nil
      iex> unless(false, "Hello")
      "Hello"

  """
  defmacro unless(clause, options) do
    do_clause   = Keyword.get(options, :do, nil)
