Eliminating double-barrel indexing, closes #3628 -- again

Author: JJ

doc/Language/variables.pod6

@@ -1226,7 +1226,7 @@ C<$?FILE> and C<$?LINE> are also available from L<CallFrame|/type/CallFrame> as
 the L<C<file>|/type/CallFrame#method_file> and
 L<C<line>|/type/CallFrame#method_line> methods, respectively.
 
-=head3 X<%?RESOURCES>
+=head3 C<%?RESOURCES>
 
 C<%?RESOURCES> is a compile-time variable available to the code of a
 X<Distribution>.