[S02] fix tiny typo

Author: Carl Masak

S02-bits.pod

@@ -3548,7 +3548,7 @@ both a string and a number.  See L<Allomorphic value semantics> below.
 
 =head3 Explicit Parcel construction
 
-As the previous section show, a parcel is not automatically constructed
+As the previous section shows, a parcel is not automatically constructed
 by parens; the parcel is actually constructed by the comma, not by
 the parens.  To force a single value to become a composite object in
 item context, either add a comma inside parens, or use an appropriate