Add 'when' variant.

pep-0308.txt

@@ -153,6 +153,18 @@ Variations
     to several people.  They all thought that if C was false, it would
     leave x unchanged.  So don't even think about this one!
 
+    ---
+
+    Another variant proposes to use 'when' instead of 'if':
+
+        <expression1> when <condition> else <expression2>
+
+    I don't see the advantage of 'when' over 'if'; it adds a new
+    keyword which is a major extra hurdle to introduce this.  I think
+    that using a different keyword suggests that the semantics are
+    different than those of an 'if' statement; but they really aren't
+    (only the syntax is different).
+
 
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