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.