# 命名空间（Namespace）
package MyApp::Utils;

use strict;
use warnings;

our $VERSION = "1.00";

sub hello {
    my ($name) = @_;
    return "Hello, $name!";
}

# 包内函数是完全限定名
# MyApp::Utils::hello("World")

1;   # 模块必须返回真值

# 包名使用 :: 分隔
package MyApp::Core::Database;      # 对应文件 MyApp/Core/Database.pm

# 变量在包空间内
package Config;
our $debug = 1;                     # $Config::debug

package main;                       # 默认包
print $Config::debug, "\n";         # 1

# use — 编译时加载并导入
use List::Util qw(max min sum);
print max(1, 2, 3), "\n";

# require — 运行时加载
require List::Util;
print List::Util::max(1, 2, 3), "\n";

# 动态加载
my $module = "JSON::XS";
my $file = "$module.pm";
$file =~ s{::}{/}g;
require $file;

# 查看模块搜索路径
perl -e 'print join "\n", @INC, "\n"';

# 运行时添加路径
use lib "/home/user/mylibs";
use lib "/opt/perl/site/lib";

# 环境变量
# export PERL5LIB="/extra/libs:/another/path"

# 命令行
# perl -I/path/to/libs script.pl

# lib/MyApp/Math.pm
package MyApp::Math;

use strict;
use warnings;
use Exporter 'import';

our $VERSION = "1.00";
our @EXPORT_OK = qw(add multiply PI);
our %EXPORT_TAGS = (
    all    => \@EXPORT_OK,
    basics => [qw(add multiply)],
);

use constant PI => 3.14159265358979;

sub add {
    my ($a, $b) = @_;
    return $a + $b;
}

sub multiply {
    my ($a, $b) = @_;
    return $a * $b;
}

1;   # 必须返回真值

#!/usr/bin/env perl
use strict;
use warnings;
use lib "lib";

use MyApp::Math qw(:all);

print add(3, 5), "\n";          # 8
print multiply(4, 6), "\n";     # 24
print PI, "\n";                  # 3.14159265358979

package MyModule;
use Exporter 'import';

our @EXPORT      = qw(always_imported);      # 自动导入（不推荐）
our @EXPORT_OK   = qw(optional_func);        # 按需导入（推荐）
our %EXPORT_TAGS = (
    utils => [qw(func1 func2)],
    all   => [qw(func1 func2 optional_func)],
);

# 使用时：
use MyModule;                          # 导入 @EXPORT
use MyModule qw(optional_func);       # 导入指定函数
use MyModule qw(:utils);              # 导入标签组
use MyModule qw(:all);                # 导入所有
use MyModule ();                      # 不导入任何符号

use ExtUtils::MakeMaker;

WriteMakefile(
    NAME         => 'MyApp::Utils',
    VERSION_FROM => 'lib/MyApp/Utils.pm',
    ABSTRACT     => 'Utility functions for MyApp',
    AUTHOR       => 'Your Name <[email protected]>',
    LICENSE      => 'perl_5',
    PREREQ_PM    => {
        'JSON::XS'    => '4.0',
        'Try::Tiny'   => '0.30',
    },
    TEST_REQUIRES => {
        'Test::More'  => '0.96',
    },
);

# lib/MyApp/Config.pm
package MyApp::Config;

use strict;
use warnings;
use Exporter 'import';
use JSON::XS;
use File::Basename;

our @EXPORT_OK = qw(load_config get_config);
our $VERSION = "1.00";

my %CONFIG;

sub load_config {
    my ($file) = @_;
    die "配置文件不存在: $file\n" unless -f $file;

    open my $fh, '<:encoding(UTF-8)', $file
        or die "无法打开 $file: $!\n";
    local $/;
    my $json = <$fh>;
    close $fh;

    %CONFIG = %{decode_json($json)};
    return \%CONFIG;
}

sub get_config {
    my ($key, $default) = @_;
    return $CONFIG{$key} // $default;
}

1;