 
   In the example above, we match `thing` against each clause "head"
   and execute the clause "body" corresponding to the first clause
-  that matches. If no clause matches, an error is raised.
+  that matches.
+
+  If no clause matches, an error is raised.
+  For this reason, it may be necessary to add a final clause, equal to `_`,
+  which will always match.
+
+      x = 10
+
+      case x do
+        0 ->
+          "This clause won't match"
+        _ ->
+          "This clause would match any value (x = #{x})"
+      end
+      #=> "This clause would match any value (x = 10)"
 
   ## Variables handling
 

  the value of `lucky?`. In case `value` has no previous value before
  case, clauses that do not explicitly bind a value have the variable
  bound to `nil`.
  """
  defmacro case(condition, clauses)


        true ->
          "This will"
      end
      #=> "This will"

  """
  defmacro cond(clauses)
