The PDL test scripts should check that Proj4 actually works correctly. In particular, if proj4 is missing the data files, "make test" just dies and PDL won't install.
Steps to reproduce:
1. Use Fedora Core 13.
2. yum install gcc cpan netpbm proj-devel
3. cpan CHM/PDL-2.4.6_991.tar.gz
The output of "make test" is attached.