Really? It should:

-C [number/list]

The -C flag controls some of the Perl Unicode features.

As of 5.8.1, the -C can be followed either by a number or a list of op
+tion letters. The letters, their numeric values, and effects are as f
+ollows; listing the letters is equal to summing the numbers.
    I     1   STDIN is assumed to be in UTF-8
    O     2   STDOUT will be in UTF-8
    E     4   STDERR will be in UTF-8
    S     7   I + O + E
    i     8   UTF-8 is the default PerlIO layer for input streams
    o    16   UTF-8 is the default PerlIO layer for output streams
    D    24   i + o
    A    32   the @ARGV elements are expected to be strings encoded
              in UTF-8
    L    64   normally the "IOEioA" are unconditional,
              the L makes them conditional on the locale environment
              variables (the LC_ALL, LC_TYPE, and LANG, in the order
              of decreasing precedence) -- if the variables indicate
              UTF-8, then the selected "IOEioA" are in effect
    a   256   Set ${^UTF8CACHE} to -1, to run the UTF-8 caching code i
+n
              debugging mode.

For example, -COE and -C6 will both turn on UTF-8-ness on both STDOUT 
+and STDERR. Repeating letters is just redundant, not cumulative nor t
+oggling.

The io options mean that any subsequent open() (or similar I/O operati
+ons) will have the :utf8 PerlIO layer implicitly applied to them, in 
+other words, UTF-8 is expected from any input stream, and UTF-8 is pr
+oduced to any output stream. This is just the default, with explicit 
+layers in open() and with binmode() one can manipulate streams as usu
+al.

-C on its own (not followed by any number or option list), or the empt
+y string "" for the PERL_UNICODE environment variable, has the same e
+ffect as -CSDL. In other words, the standard I/O handles and the defa
+ult open() layer are UTF-8-fied but only if the locale environment va
+riables indicate a UTF-8 locale. This behaviour follows the implicit 
+(and problematic) UTF-8 behaviour of Perl 5.8.0.
[download]

Maybe you should perlbug the error.