Thank you that worked a treat, it seems to get a bit further along with executing the script now but crashes out further on now with this error message

Scanning cache y/build for sizes
gzip: y/sources/authors/id/A/AN/ANDK/CPAN-1.70.tar.gz: No such file or
+ directory
CPAN.pm needs either both external programs tar and gzip installed or
both the modules Archive::Tar and Compress::Zlib. Neither prerequisite
is available. Can't continue.
[download]

now I did the same for tar as I did for gzip in
/usr/lib/perl5/5.8.0/CPAN/Config.pm
, but I don't know what syntax I use to get the modules installed.