OS X 上的 Perl Unicode 测试在 Debian 上失败

我有以下测试：

use Test::More;
use Lingua::EN::NameCase 'nc';
use utf8;
my $output = Test::Builder->new->todo_output;
binmode $output, ':encoding(UTF-8)';
$output = Test::Builder->new->failure_output;
binmode $output, ':encoding(UTF-8)';

my $name = 'Lintão';
is nc($name), $name, 'nc() should not change a properly namecased name';
diag nc($name);

done_testing;

在装有 Perl 5.10.1 的 Mac OS X 上，我得到以下输出：

nc.t ..
ok 1 - nc() should not change a properly namecased name
1..1
# Lintão
ok
All tests successful.
Files=1, Tests=1,  0 wallclock secs ( 0.02 usr  0.01 sys +  0.04 cusr  0.00 csys =  0.07 CPU)
Result: PASS

不幸的是，在 Debian Squeezebox 上使用 5.10.1 Perl 进行的相同测试会产生以下输出：

nc.t ..
not ok 1 - nc() should not change a properly namecased name

#   Failed test 'nc() should not change a properly namecased name'
#   at nc.t line 10.
#          got: 'LintãO'
#     expected: 'Lintão'
# LintãO
1..1
# Looks like you failed 1 test of 1.
Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/1 subtests

Test Summary Report
-------------------
nc.t (Wstat: 256 Tests: 1 Failed: 1)
  Failed test:  1
  Non-zero exit status: 1
Files=1, Tests=1,  0 wallclock secs ( 0.01 usr  0.00 sys +  0.03 cusr  0.00 csys =  0.04 CPU)
Result: FAIL

中的违规行nc()子程序看起来是这样的：

s{ \b (\w)   }{\u$1}gox ;           # Uppercase first letter of every word.

因此，不知何故，Debian 上相同版本的 Perl 出现了单词边界错误。谁能帮我进一步调试吗？

Linux 机器上的区域设置不考虑ã一个单词字符 (Lingua::EN::NameCase has use locale;所以它使用当前LC_CTYPE字符分类设置）。使用 perl 酿造的珍珠从 5.8.1 到 5.18.1，我在 Ubuntu 12.04 LTS 上一致地得到这个输出en_GB.UTF-8 locale:

$ perl -Mutf8 -le 'print 0+("ã" =~ /\w/); use locale; print 0+("ã" =~ /\w/)'
1
0