【Perl读书笔记】defined函数

读 《C程序员精通Perl》http://book.douban.com/subject/1232075/   2.4.4节 笔记

#!/usr/bin/perl
use strict;
use warnings;

my $name = "calf_man";
my $value;

if (defined($name)) {
        print "The name is defined as $name\n";
}

if (not defined($value)) {
        print "The value is not defined.\n";
}

#$name = undef; 
undef($name);
#undef #name;
if (not defined($name)) {
        print "The name is not defined.\n";
}

运行结果：

[root@localhost perl_practice]# ./define.pl   
The name is defined as calf_man
The value is not defined.
The name is not defined.
[root@localhost perl_practice]#