The first thing I would do is not try to install the Cv module with the sudo step. I always do

$ sudo su
...
# cpan
cpan> install Cv
...
[download]

because I feel like I have a bit more control in case something goes awry. If something does go wrong, as in this case, I go to another terminal window for possible remediation. In your case you may have a problem with OpenCV not being compatible with the latest Ubuntu (the OpenCV site says it was tested with Ubuntu 10.04 which is quite old and gcc has advanced a lot since then). I would consult with the OpenCV group if you can't fix the problem yourself.

UPDATE: The Ubuntu site has a blurb on installing OpenCV with Ubuntu 14.04.