With Perl6, few people will compile whole librairies but most
will load bytecode. At this late stage there is little place for
tunable optimization except JITting or it would defeat the
sharing of such code between different intances of Perl6. Nothing
will preclude to dynamically extend classes. I note that in Perl6
many optimizations were autoloading for deferring compilation of
material until it's really needed. With bytecode, it makes sense
(at least optimization-wise) that the programmer decides if his
classes will be sealed or some methods to be final because at the
user level it is too late to decide.

--
 stef