Some modifications for haskell-to-p6

- { * } doesn't become { $_ }, it returns a Whatever
- Remove the explicit smartmatch
- Mention the defined-or operator

Author: CIAvash

doc/Language/haskell-to-p6.pod6

@@ -60,7 +60,7 @@ and Undefined objects. Plain type objects are undefined while instansiated objec
     sub parse-int(Str $s --> Int) { ... }
     
     given parse-int($string) {
-      when Int:D { * }
+      when Int:D { $_ }
       when Int:U { 0 }
     }
     
@@ -79,8 +79,8 @@ that specifically test for definedness.
     
     # One way to do it
     given parse-int($string) {
-      when * ~~ Int:D { * }
-      when * ~~ Int:U { 0 }
+      when Int:D { $_ }
+      when Int:U { 0 }
     }
     
     # Another way to do it
@@ -89,7 +89,10 @@ that specifically test for definedness.
     
     
     # A better way
-    with parse-int($string) { * } else { 0 }
+    with parse-int($string) { $_ } else { 0 }
+
+    # With the defined-or operator
+    parse-int($string) // 0
     
 The `with` operator that you see above is like `if`, except it explicitly tests for definedness and then
 passes the result to the following block. Similarly, `without` tests that the object is undefined and also