#!/usr/bin/perl
 
$txt="ab\ncd";
$txt =~ /a.*c/m;        # 匹配失败
print "===match start===\n$&\n===match end===\n";

$txt="ab\ncd";
$txt =~ /a.*c/ms;       # 匹配成功
print "===match start===\n$&\n===match end===\n";