Progress so far...

5.12.3 build is being painful, but there is progress. I got a quick response from the maintainers of the Math::Big* modules on one issue, but there's another I haven't reported to them yet - nor do I know whether it's their issue or mine! Math::BigInt::GMP is ABENDing during its tests. This could be caused by the build of libgmp I'm using, (which was built from a mercurial checkout from last year) so I'm going to put fixing that off until after Beta 1, and just skip it for now... problem being that it's near the bottom of a dependency tree, so all those modules will have to be yanked for Beta 1.

But at least a build of Strawberry Perl 5.12.3 will be available to investigate with!