+Remind that for C<perl> to be able to parse C<my Str $x>, you need :
+
+=over 4
+
+=item *
+
+either the C<Str> package to be defined ;
+
+=item *
+
+or for C<Str> to be a constant sub returning a valid defined package.
+
+=back
+
+so make sure you follow one of those two strategies to define your types.
+
+This pragma is B<not> implemented with a source filter.