[S09] be more clear about what's an error

Two of the three examples marked with "Error" turned out to actually
be logical maybe-not-what-I-meant errors. Marked them as such.

S09-data.pod

@@ -207,8 +207,8 @@ specification, but "unspace" is allowed:
 Note that the square brackets are a compile-time declarator, not a run-time
 operator, so you can't use the "dotted" form either:
 
-    my @values.[10];          # Error
-    my @keys\ .[10];          # Error
+    my @values.[10];          # An indexing, not a fixed-size declaration
+    my @keys\ .[10];          # Ditto
 
 Attempting to access an index outside an array's defined range will fail: