Attempt clarifying the pin operator

lib/koans/07_pattern_matching.ex

@@ -8,12 +8,14 @@ defmodule PatternMatching do
   koan "A pattern can change" do
     a = 1
     a = 2
-    assert (a == 2) == ___
+    assert a == ___
   end
 
   koan "A pattern can also be strict" do
     a = 1
-    assert ^a = ___
+    assert_raise ___, fn() ->
+      ^a = 2
+    end
   end
 
   koan "Patterns can be used to pull things apart" do

test/koans/patterns_koans_test.exs

@@ -5,8 +5,8 @@ defmodule PatternsTests do
   test "Pattern Matching" do
     answers = [
       1,
-      true,
-      1,
+      2,
+      MatchError,
       {:multiple, [1, [2,3,4]]},
       [1,2,3,4],
       3,