Improve circumfix entry a bit.

Author: pmichaud

S99-glossary.pod

@@ -204,7 +204,7 @@ splice will be very difficult for the end-user to notice in day-to-day use.
 =head2 circumfix
 
 If a syntactic construct, for example a pair of parenthesis, surrounds another
-piece of syntax, that first part is called a circumfix.
+piece of syntax, the surrounding first part is called a circumfix.
 
     say (2 + 3);
       # ^^^^^^^ circumfix