cpan : Net::IDN::Encode 中文域名punycode转换
$in 为命令行输入的中文域名，例如
海底捞.中国 => xn–fxt99hsvk.xn–fiqs8s.
#!/usr/bin/perl
use Encode;
use Encode::Locale;
use Net::IDN::Encode ':all';
use utf8;
my ($in) = @ARGV;
my $unicode = decode(locale=>$in);
my $e = domain_to_ascii($unicode);
print $e,"\n";