[S06] only add @_ and %_ to default sig if actually used in body

git-svn-id: http://svn.pugscode.org/pugs@27801 c213334d-75ef-0310-aa23-eaa082d1ae64

S06-routines.pod

@@ -15,8 +15,8 @@ Synopsis 6: Subroutines
 
     Created: 21 Mar 2003
 
-    Last Modified: 26 Jun 2009
-    Version: 110
+    Last Modified: 29 Jul 2009
+    Version: 111
 
 
 This document summarizes Apocalypse 6, which covers subroutines and the
@@ -125,10 +125,15 @@ You can declare a sub without parameter list, as in Perl 5:
 
     sub foo {...}
 
-This is equivalent to
+This is equivalent to one of:
 
+    sub foo () {...}
+    sub foo (*@_) {...}
+    sub foo (*%_) {...}
     sub foo (*@_, *%_) {...}
 
+depending on whether either or both of those variables are used in the body of the routine.
+
 Positional arguments implicitly come in via the C<@_> array, but
 unlike in Perl 5 they are C<readonly> aliases to actual arguments: