Build in the usual way:

perl Makefile.PL
make test
make install

For that to work, you'll need a compiler that provides support for the _Decimal64 type.

My (mingw64.sf) ports of gcc-4.6.3 and gcc-4.7.0 provided such support, but my (mingw.org)
port of gcc-4.5.2 did not.

If your compiler provides the strtod64 function and you want to make use of it, either
provide the Makefile.PL with the command line argument STRTOD64=1, or edit the Makefile.PL
to set $strtod64 to 1.

Consider this module to be alpha software.

Cheers,
Rob