in reply to Why upgrade perl?
5.16+ has much better Unicode support than 5.10.1, including the "unicode_strings" feature (where all strings are treated as Unicode except in the scope of use bytes or use locale), and the fc function which is useful for case-insensitive string comparisons.
Perl 5.16 has the __SUB__ keyword which acts as a coderef pointing to the current sub. This is useful for writing anonymous recursive functions.
5.14+ supports the package NAME BLOCK syntax, which is cute, but isn't going to change your world.
use v5.12 (or above) automatically enables use strict, reducing some typing.
The yada-yada operator, introduced in Perl 5.12 is handy during development.
There are beginning to be a few nice CPAN modules like Switch::Plain, Fun and Try that use the pluggable keyword API introduced in Perl 5.12/5.14.
Whether these are compelling enough reasons to upgrade will depend a lot on how you use Perl, and what you use it for. I'd certainly suggest having a copy of Perl 5.18 on a development machine to make sure that the code you write runs on it; whether you deploy it for production use is a different matter though.