为什么这个带有2字节unicode字符的正则表达式会在匹配时为左值发出“未初始化”警告？

The following code:

以下代码：

#!/usr/bin/env perl
use utf8;
use strict;
use warnings;
use 5.012; # implicitly turn on feature unicode_strings
my $test = "some string";
$test =~ m/.+\x{2013}/x;
#!/usr/bin/env pe