new version is out: Number-Format-1.61a the package builds fine after copying the ebuild Portage 2.1.6.4 (default/linux/amd64/2008.0, gcc-4.3.2, glibc-2.8_p20080602-r0, 2.6.28-rc8-zen1 x86_64) perl-5.8.8-r5