add a loop in the mutable-references example

mutable-references.hs

@@ -1,6 +1,8 @@
 import Control.Monad.STM
 import Control.Concurrent.STM.TVar
 
+import Data.Foldable (for_)
+
 main =
   do
     a <- atomically (newTVar 3)
@@ -34,8 +36,8 @@ main =
               writeTVar ref2 x1
 
     increment a
-    increment a
-    increment b
+    for_ [1..5] $ \_ ->
+        increment b
     printVars "incremented"
 
     swap a b

outputs/mutable-references.txt

@@ -1,5 +1,5 @@
 a = 3, b = 5 (initial values)
 a = 7, b = 5 (changed a to 7)
 a = 7, b = 10 (doubled b)
-a = 9, b = 11 (incremented)
-a = 11, b = 9 (swapped)
+a = 8, b = 15 (incremented)
+a = 15, b = 8 (swapped)