New features in Perl are not enabled, by default, for backward compatibility reasons.
This is often useful if you need to check the current Perl version before using library modules that won't work with older versions of Perl. (We try not to do this more than we have to.)
Also, if the specified Perl version is greater than or equal to 5.9.5, use VERSION will also load the feature pragma and enable all features available in the requested version. See feature.
Similarly, if the specified Perl version is greater than or equal to 5.11.0, strictures are enabled lexically as with use strict (except that the strict.pm file is not actually loaded).
A newer version of Perl has not yet been approved/committed for 12.04, 12.10, or even 13.10. See the main Ubuntu page for Perl here. However, it does look like there is some activity with work moving forward with Perl 5.17.
You could install from source, but I would not recommend over riding the system Perl installation. Instead, I would recommend installing a sandboxed version using PerlBrew.