DBC is integral to Perl 6
Since the subject's come up ;-)
PRE and POST will obviously handle pre-/post-conditions for methods. However - I've not spotted an easy way of expressing class invariants. Is there something that I've missed?
Also, there do not appear be a built ins for dealing with naming conflicts as there are in languages like Eiffel. How would I rename method foo() to bar() in a sub-class and keep the pre- and post-conditions?
Disclaimer: I've still not read A12 properly, so apologies if the answer is in there and I missed it when I skimmed it :-)