I've recently released a development snapshot of Module::Build 0.35_01. This release implements MYMETA.yml.
MYMETA.yml is just like META.yml, in that it follows the CPAN Meta Spec, but whereas META.yml is generated by the distribution author at packaging time, MYMETA.yml is generated by the end user at configure time after any dynamic dependencies are known.
This is the new approach agreed to in previous Perl QA Hackathons for how configuration tools will communicate dependency information to installers and other toolchain modules. Recent versions of CPAN.pm (including the version released with Perl 5.10.1) already support MYMETA.yml and support should be available soon in CPANPLUS.
In the meantime, you can install Module::Build 0.35_01 to see how MYMETA.yml will work.
$ cpan DAGOLDEN/Module-Build-0.35_01.tar.gz