On many systems, including many systems including Fedora 19 Linux, there is no "f77" nor "g77" executable. The most common FORTRAN -- gfortran - isn't recognized by ExtUtils::F77 (current as of 15-Nov-2013), so ExtUtils::F77 fails. But ExtUtils::F77 is still listed as a prerequisite in the package metadata in CPAN. In turn, that means PDL installation fails by default on those systems.
I'm filing an F77 bug with KGB too -- but if we don't actually need FORTRAN for core functionality we should remove it from the prerequisites.