Your problem is not that it can't find cpan2rpm, it can find it just fine, but this:

Tarball extraction: [%(eval/%(eval/rpms/SOURCES/XML-DOM-1.41.tar.gz]
sh: -c: line 1: syntax error near unexpected token `%(e'
sh: -c: line 1: `tar -xz --directory /tmp/cpan2rpm -f %(eval/%(eval/rp
+ms/SOURCES/XML-DOM-1.41.tar.gz'
[download]

And variations thereon. cpan2rpm is trying to operate on files called %(eval/%(eval etcetera. These files do not exist. Apparently, something has gone wrong in cpan2rpm - it looks like those sequences are meant to be paths to your rpms directory, but somehow things got garbled. I would suggest having a look in cpan2rpm, near lines 223 and 694 to see how these values are supposed to be filled in.

CU
Robartes-