PerlTypeglob，Typeglob引用，文件句柄和常量
示例
一个类型团*foo持有到的内容引用全球使用该名称的变量：$foo，@foo，$foo，&foo，等你可以像一个哈希访问，并分配给直接操作符号表（恶！）。
use v5.10; # necessary for say
our $foo = "foo";
our $bar;
say ref *foo{SCALAR}; # SCALAR
say ${ *foo{SCALAR} }; # bar
*bar = *foo;
say $bar; # bar
$bar = 'egg';
say $foo; # egg处理文件时，通常会处理Typeglob。open例如，当被要求创建非全局文件句柄时，生成对typeglob的引用：
use v5.10; # necessary for say
open(my $log, '> utf-8', '/tmp/log') or die $!; # open for writing with encoding
say $log 'Log opened';
# You can dereference this globref, but it's not very useful.
say ref $log; # GLOB
say (*{$log}->{IO} //'undef'）;＃undef
close $log or die $!;Typeglobs也可以用于创建全局只读变量，尽管useconstant使用范围更广。
# Global constant creation
*TRUE = \('1');
our $TRUE;
say $TRUE; # 1
$TRUE = ''; # dies, "Modification of a read-only value attempted"
# use constant instead defines a parameterless function, therefore it's not global,
# can be used without sigils, can be imported, but does not interpolate easily.
use constant (FALSE => 0);
say FALSE; # 0
say &FALSE; # 0
say "${\FALSE}"; # 0 (ugh)
say *FALSE{CODE}; # CODE(0xMA1DBABE)
# Of course, neither is truly constant when you can manipulate the symbol table...
*TRUE = \('');
use constant (EVIL => 1);
*FALSE = *EVIL;