Data::Dumper模块使用小例

最近用了一把Data::Dumper模块，感觉很好很强大，故写了个小例子。

Data::Dumper模块主要用途是：给出一个或多个变量，包括引用，以PERL语法的方式返回这个变量的内容。
比方说，这里有个很复杂的hash，数据结构很复杂，我想看看这个hash里面的内容。除了常见的方式（直接
用print或者编历keys然后打印）， 我们也可以使用Data::Daumper->Dump([\%hash])的形式。同时，
模块中定义了很多的配置参数，让用户可以调整打印格式。

简单列举几个（具体参见perldoc），这些变量在模块
$Data::Dumper::Indent
这个设置打印的缩进格式，可以设置成0,1,2和3。用户可以自己尝试下。
$Data::Dumper::Terse
如果设置这个变量，则不打印变量的名字，只打印变量的内容。
$Data::Dumper::Maxdepth
不超过这个变量的限制深度，才打印变量的内容。

下面写个程序说明问题：

#!/usr/bin/perl

use strict;
use warnings;

use Data::Dumper;

my %people = (
    'name' => 'ray',
    'age' => 24,
    'sex' => 'man',
    'food' => ['egg', 'apple'],
);

# See Data::Dumper module to get the default vaule of the
# following module gobal variable. You can overwrite the
# default value to user defined one.

print "Show perl hash, with pre-defined variable name\n ";
print "and without maxdepth\n";
$Data::Dumper::Terse = 0; # default is 0
$Data::Dumper::Indent = 3; # default is 2
$Data::Dumper::Maxdepth = 0; # default is 0
my $variable_name = '*' . "my_info";
print Data::Dumper->Dump([\%people], [$variable_name]);

print "Show perl hash, without pre-defined variable name\n ";
print "and with maxdepth is 1\n";
$Data::Dumper::Terse = 1; # default is 0
$Data::Dumper::Indent = 2; # default is 2
$Data::Dumper::Maxdepth = 1; # default is 0
$variable_name = '$' . "my_info";
print Data::Dumper->Dump([\%people], [$variable_name])

ray@localhost perl]$ perl data_dumper.pl
Show perl hash, with pre-defined variable name
 and without maxdepth
%my_info = (
             'food' => [
                         #0
                         'egg',
                         #1
                         'apple'
                       ],
             'name' => 'ray',
             'sex' => 'man',
             'age' => 24
           );
Show perl hash, without pre-defined variable name
 and with maxdepth is 1
{
             'food' => 'ARRAY(0x91d68c4)',
             'name' => 'ray',
             'sex' => 'man',
             'age' => 24
           }