关于GetOptions的介绍，请参照官方文档（link）

The Getopt::Long module implements an extended getopt function called GetOptions(). It parses the command line from @ARGV , recognizing and removing specified options and their possible values.

This function adheres to the POSIX syntax for command line options, with GNU extensions. In general, this means that options have long names instead of single letters, and are introduced with a double dash "--". Support for bundling of command line options, as was the case with the more traditional single-letter approach, is provided but not enabled by default.

简单讲，就是执行脚本给定参数为长参（--verbose）或短参(-v)都可以接受和识别。(--verbose和-v实际上作用相同)

举个例子：

use strict;

use Getopt::Long;

my $verbose = '';

GetOptions("verbose" => \$verbose) or die ("Invalid arguments.\n");
	
if ($verbose){
	print "\$verbose received\n";
} else {
	print "No expected arguments\n";
}

--v 可识别

--verbose 可识别

传其它参数，比如-balabala。（不可识别并报错）