clarify that this section is only about *pre-defined* dynamic variables

Author: schultzdavid

doc/Language/variables.rakudoc

@@ -1525,8 +1525,8 @@ sub get-file-content {
 
 =head2 Dynamic variables
 
-All dynamically scoped variables have the C<*> twigil, and their name is
-(conventionally) written in uppercase.
+The pre-defined dynamically scoped variables all have the L<C<*> twigil|#The_*_twigil>,
+and their name is (conventionally) written in uppercase.
 
 X<|Variables,$*ARGFILES>X<|Variables,@*ARGS>
 =head3 Argument related variables
@@ -1867,7 +1867,7 @@ To activate this only for a lexical scope:
 my $*RAT-OVERFLOW = FatRat;
 =end code
 
-How does that work? The $*RAT-OVERFLOW variable is supposed to contain
+How does that work? The C<$*RAT-OVERFLOW> variable is supposed to contain
 a class or instance on which the C<UPGRADE-RAT> method will be called
 when a Rat overflows. So you can introduce your own behavior by
 creating a class with an C<UPGRADE-RAT> method in it.