Perl Symbolic Reference
看一些模块的代码，很多时候通过*glob的方式来改变变量或者函数，这种方法称为Symbolic reference。首先看一下*glob的结构，这个在之前的博文已经讲过，不做细述：
SV = PVGV(0x18d1364) at 0x182aaec
REFCNT = 2
FLAGS = (IN_PAD)
NAME = "test"
NAMELEN = 4
GvSTASH = 0x298fc4"main"
GP = 0x18b90ac
SV = 0x0
REFCNT = 1
IO = 0x0
FORM = 0x0
AV = 0x0
HV = 0x0
CV = 0x0
CVGEN = 0x0
LINE = 4
FILE = "test.pl"
FLAGS = 0x8
EGV = 0x182aaec"test"
运行下边的代码段，察看一下输出对应的ref slot。
print ref \1;
print ref \'testing';
print ref ;
print ref {};
print ref sub {};
如何给*glob赋值？通过下面的方式，填充Symbol的不同slot，从而使得对应的$test,@test,%test,&test非空。
use Data::Dumper;
use Devel::Peek;
*test = \1;
*test = ;
*test = {qw(one two three four)};
*test = sub {};
print Dump *test;
SV = PVGV(0x18d134c) at 0x182aaec
REFCNT = 6
FLAGS = (MULTI,ASSUMECV,IN_PAD)
NAME = "test"
NAMELEN = 4
GvSTASH = 0x298fc4"main"
GP = 0x18b9104
SV = 0x182aadc
REFCNT = 1
IO = 0x0
FORM = 0x0
AV = 0x2990d4
HV = 0x299214
CV = 0x18b1e7c
CVGEN = 0x0
LINE = 4
FILE = "test.pl"
FLAGS = 0xe
EGV = 0x182aaec"test"
如何使用？use strict情况下有几种方式：
下面的情况直接调用Symbol或者通过our定义直接访问变量，函数无需our定义，总是一个Symbol，可以直接通过名字访问。
use strict;
use Data::Dumper;
use Devel::Peek;
*test = \1;
*test = ;
*test = {qw(one two three four)};
*test = sub {print "testing\n";};
print $::test;
print %::test;
&test();
our ($test, %test);
print $test;
print %test;
&test;
如果通过一个变量传名字访问另外一个变量，则需要通过下面的方式no strict 'refs'。
no strict 'refs';
print ${'test'};
print %{'test'};
&{'test'};
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