As I alluded to, with 5.8.1,
-C enable native wide character system interfaces
-C[number/list] enables the listed Unicode features
and it would be better, IMO, to show the newer --help.
From the perldelta for 5.8.1:
The -C Switch Has Been Repurposed
The -C switch has changed in an incompatible way. The old semantics
of this switch only made sense in Win32 and only in the "use utf8"
universe in 5.6.x releases, and do not make sense for the Unicode
implementation in 5.8.0. Since this switch could not have been used
by anyone, it has been repurposed. The behavior that this switch
enabled in 5.6.x releases may be supported in a transparent,
data-dependent fashion in a future release.
For the new life of this switch, see perl581delta "UTF-8 no longer default under
UTF-8 locales", and perlrun/-C.