This module applies specifically to the "double-double" long double arrangement - such as
provided by the PowerPC processors.
Install in the usual way:
perl Makefile.PL
make test
make install
If your perl's NV (float) is not such a 'double-double', the Makefile.PL should detect
this and refuse to create a makefile - and you won't be able to build and install this
module using that perl.
That's the way it should work, anyway. Please file a bug report if you strike deviant
behaviour.