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 [qw(one, two ,three)];

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 = [qw(one two three)];

*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 = [qw(one two three)];

*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'};