来自perldoc
perlsyn关于Foreach循环的主题：
If the variable was prevIoUsly
declared with my,it uses that
variable instead of the global one,
but it’s still localized to the loop.
但请考虑这个例子：
use Devel::Peek;
my $x = 1;
Dump $x;
for $x ( 1 ) { Dump $x }
SV = IV(0x8117990) at 0x8100bd4
REFCNT = 1
FLAGS = (PADBUSY,PADMY,IOK,pIOK)
IV = 1
SV = IV(0x8117988) at 0x8100bf8
REFCNT = 2
FLAGS = (IOK,READONLY,pIOK)
IV = 1
看起来这些变量并不相同.这是文档中的错误,还是我错过了什么？
解决方法
每个规则都需要它的例外,这是一个.在for循环中,如果循环变量是词法(用my声明),Perl将为循环中的当前项创建一个新的词法别名. OP代码可以写成如下：
use Data::Alias 'alias';
my $x = 1;
for (2..3) {
alias my $x = $_;
# note that $x does not have dynamic scope,and will not be visible in
# subs called from within the loop
# but since $x is a lexical,it can be closed over
}