I had a similar problem and followed a different path: in my virtual Mint 15 I installed a new perl (5.14.4) over the native perl 5.14.2 and apt-get started throwing errors, mainly...
...dont't find ... Debconf/Db.pm in @INC ...

So @INC has lost the directory which holds that pm, but it (and other pms) were still in the system.

Solution: find Db.pm
find . -name Db.pm -print
>>>/usr/share/perl5/Debconf/Db.pm

Then I go to one of the dirs in current @INC and create a symlink
cd /usr/lib/perl5/site_perl/5.14.4/
ln -s /usr/share/perl5/Debconf Debconf

'et voila', I managed to upgrade flawlessly, apt-get is working
apt-get update
apt-get upgrade

Don't know if it would work if both perl major versions were different (here is 5.14 for both).