I'm not sure that it's necessary to fix your Ubuntu installation but you will probably run into problems down the road if you don't. It used to be that your package manager would be broken by now but apt has been moving away from the perl dependency so you might not ever notice. At the very least, perl programs installed through the package manager will be broken.
which should say something like/usr/bin/perl -v
You can also check to see what kind of file it is withThis is perl, v5.10.1 (*) built for x86_64-linux-gnu-thread-multi
which should say something likefile /usr/bin/perl
If your system doesn't give similar responses, your system perl is broken./usr/bin/perl: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dy +namically linked (uses shared libs), for GNU/Linux 2.6.18, stripped