But there is no bufferoverflowU stuff in Makefile.PL
in reply to Re^3: Installing Tk problems with Active State on Windows
in thread Installing Tk problems with Active State on Windows
Correct. It's to be found in perl/lib/Config_heavy.pl - so remove all (2, I think) occurrences of bufferoverflowU.lib from that file to fix that problem.
But, unlike 32-bit ActivePerl and 32-bit MinGW, 64-bit ActivePerl won't work with 64-bit MinGW straight out of the box. (ExtUtils::FakeConfig needs to be installed.)