perlrun:
As of 5.8.1, the -C can be followed either by a number or a list of option letters.

perlrun:
Note: Since perl 5.10.1, if the -C option is used on the #! line, it must be specified on the command line as well

perlretut:
The //a modifier, available starting in Perl 5.14, is used to restrict the matches of \d, \s, and \w to just those in the ASCII range.