Question

所以，在Strawberry Perl中，％ENV似乎是一个普通的哈希（至少它没有绑定），但它似乎也解决了密钥不敏感的问题。鉴于环境，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环境变量和案例）。所以，我想知道％ENV如何同时成为一个普通哈希，并且具有“隐式”键，当您调用它们内置的键时，这些键未列出。％ENV哈希是否神奇而不被束缚？

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

以下是来自ActivePerl，但每个Perl包括Strawberry Perl都会给你同样的东西：

>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是神奇的。但它并没有束缚;这将是魔术类型“P”而不是“E”。

Answer 2

％ENV哈希是否神奇而不被束缚？

是的，％ENV是一个不受束缚的魔术变量，类似于其他各种变量，如％SIG。有关其中的更多信息，请参阅perldoc perlvar。

草莓Perl是％ENV一个普通的对象

2 个答案: