windows - Strawberry Perl 是 %ENV 一个普通的对象

Question

因此，在 Strawberry Perl 中，%ENV 似乎是一个普通的散列(至少它没有绑定(bind))，但它似乎也不区分大小写地解析键。考虑到环境，这是有道理的变量在 PowerShell 中不区分大小写(我不确定它们之间的确切关系Windows 环境变量和大小写)。所以，我想知道 %ENV 如何同时成为普通散列，并具有“隐式”键，当您称它们为内置键时，这些键未列出。%ENV hash 不用绑定(bind)就神奇吗？

use strict;
use warnings;

# Env appears to be an ordinary hash
# 'TEMP' is present in the list of environment variables
# but 'temp' is not
printf "$_\n" foreach keys %ENV;

print "\n";

# this gives us the value of $ENV:TEMP
# which makes sense.
printf "uppercase 'temp' maps to %s\n", $ENV{TEMP};

# even though temp is not present in the
# list of keys, the same value appears as for
# $ENV{TEMP}
# This seems to make sense given the behavior of powershell
# (I am not quite sure what the relationship is between
# Windows environment variables and case, but this seems reasonable.)
printf "lowercase 'temp' maps to %s\n", $ENV{temp};

# However, %ENV is not a tied hash.
printf "Tie status: %s\n", tied(%ENV) // "not a tied variable";

Answer 1

以下内容来自 ActivePerl，但包括 Strawberry Perl 在内的每个 Perl 都会给您同样的东西:

>perl -E"use Devel::Peek; Dump(\%ENV, 1);"
SV = IV(0x74b154) at 0x74b154
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x63e33c
  SV = PVHV(0x62a8ac) at 0x63e33c
    REFCNT = 2
    FLAGS = (SMG,RMG,SHAREKEYS)
    MAGIC = 0x639084                               <-------
      MG_VIRTUAL = &PL_vtbl_env
      MG_TYPE = PERL_MAGIC_env(E)
    ARRAY = 0x640794  (0:30, 1:22, 2:11, 3:1)
    hash quality = 107.7%
    KEYS = 47
    FILL = 34
    MAX = 63

如您所见，%ENV 很神奇。但它没有绑定(bind)；那将是魔术类型“P”而不是“E”。