Perl初学笔记之Hello World

工作需要开始学Perl，下载了个Windows版（5.16）。安装过程很常规，装好后自然就是写第一个程序了：经典的"Hello, World!"。这个输出结果看着是不是有点Python的影子？

#!/usr/bin/perl
print "Hello,World!n";

运行结果如下：

c:Perl>perl HelloWorld.pl
Hello,World!

接着顺手了解了一下cpan。尽管当时还没完全搞懂它具体是干什么的，但直觉告诉我，它应该是用来安装各种模块的工具——CPAN上的模块有9000多种。跑个命令试试看：

c:Perl>cpan App::cpanminus
Set up gcc environment - 3.4.5 (mingw-vista special r3)
CPAN: Term::ANSIColor loaded ok (v4.02)
CPAN: Storable loaded ok (v2.34)
Reading 'C:PerlcpanMetadata'
Database was generated on Fri, 07 Mar 2014 13:06:13 GMT
CPAN: Module::CoreList loaded ok (v2.80)
App::cpanminus is up to date (1.7001).

看第二次输出的结果，这玩意儿应该是类似于数据库的东西吧。安装好cpanm之后，用它来装模块就方便多了。命令格式很简单：cpanm Module::Name。试一下安装YAML：

c:Perl>cpanm YAML
Set up gcc environment - 3.4.5 (mingw-vista special r3)
--> Working on YAML
Fetching http://www.cpan.org/authors/id/I/IN/INGY/YAML-0.90.tar.gz ... OK
Configuring YAML-0.90 ... OK
Building and testing YAML-0.90 ... OK
Successfully installed YAML-0.90
1 distribution installed

如果不熟悉cpanm的用法，直接执行 cpanm --help 就能看到详细的提示信息：

c:Perl>cpanm --help
Set up gcc environment - 3.4.5 (mingw-vista special r3)
Usage: cpanm [options] Module [...]

Options:
  -v,--verbose              Turns on chatty output
  -q,--quiet                Turns off the most output

根据上面的安装过程，貌似cpanm也支持直接通过链接来安装模块。验证一下，果然可以：

c:Perl>cpanm http://search.cpan.org/CPAN/authors/id/S/SH/SHARYANTO/Alt-Base-0.02.tar.gz
Set up gcc environment - 3.4.5 (mingw-vista special r3)
--> Working on http://search.cpan.org/CPAN/authors/id/S/SH/SHARYANTO/Alt-Base-0.02.tar.gz
Fetching http://search.cpan.org/CPAN/authors/id/S/SH/SHARYANTO/Alt-Base-0.02.tar.gz ... OK
Configuring Alt-Base-0.02 ... OK
==> Found dependencies: Alt
--> Working on Alt
Fetching http://www.cpan.org/authors/id/I/IN/INGY/Alt-0.04.tar.gz ... OK
Configuring Alt-0.04 ... OK
Building and testing Alt-0.04 ... OK
Successfully installed Alt-0.04
Building and testing Alt-Base-0.02 ... OK
Successfully installed Alt-Base-0.02
2 distributions installed

学了些基础后，开始写一个文件操作的脚本。脚本里用到了 Path::Class 模块，结果一跑就报错了：

use Path::Class;
C:PerlLearn>perl FindFile.pl
Can't locate Path/Class.pm in @INC (@INC contains: C:/Perl/site/lib/MSWin32-x86-multi-thread C:/Perl/site/lib C:/Perl/lib .) at FindFile.pl line 4.
BEGIN failed--compilation aborted at FindFile.pl line 4.

提示很明确：找不到 Path::Class 模块——也就是没安装嘛。用cpanm装一下，果然问题解决了：

C:PerlLearn>cpanm Path::Class
Set up gcc environment - 3.4.5 (mingw-vista special r3)
--> Working on Path::Class
Fetching http://www.cpan.org/authors/id/K/KW/KWILLIAMS/Path-Class-0.33.tar.gz ... OK
Configuring Path-Class-0.33 ... OK
Building and testing Path-Class-0.33 ... OK
Successfully installed Path-Class-0.33
1 distribution installed

完~