实际的重命名是在下面完成的：

CORE::rename($was,$_)

您发布的是基于用户提供的代码计算新名称的代码的近似值。更好的近似值：

my $code = 's/\.bak$//'
my $sub = eval "sub { $code }"

my @args = 'a.b.c.bak'; 
for (@args) {           # Aliases `$_` to the array element.
   my $was = $_;
   $sub->();            # Probably changes `$_`.

   say "$was => $_";    # The rename would happen here.
}

如果我们把潜艇连上，

my @args = 'a.b.c.bak'; 
for (@args) {           # Aliases `$_` to the array element.
   my $was = $_;
   s/\.bak$//;          # Changes `$_`.

   say "$was => $_";    # The rename would happen here.
}