I think your problem may be in your shell config. If you look below you will see how I get two different versions of CPAN.

For my Perl 5.14

$ sudo perl -MCPAN -e shell
Password:
cpan shell -- CPAN exploration and modules installation (v1.9600)
cpan>
[download]

However, if I invoke Perl with /usr/bin/perl

$ sudo /usr/bin/perl -MCPAN -e shell
Password:
cpan shell -- CPAN exploration and modules installation (v1.7602)
cpan>
[download]

I get the CPAN that comes with my system Perl - that's probably what you want so you need to restore your shell config so it uses your system Perl. You could try this (outside the CPAN shell)

sudo /usr/bin/perl -MCPAN -e 'install File::Basename'
[download]

BTW I would highly recommend perlbrew for installing non-system Perl