my $subject = "=?GB18030?B?XXXXXXXXXX?=";

##</code><code>##


use Encode::HanExtra;


##</code><code>##


#!/usr/bin/perl
use strict;
use warnings;
use Encode qw(encode decode);
use Encode::HanExtra;
no warnings 'utf8'; 

my @subject = ("Room Rush \303\242\302\200\302\223 Enjoy 25% off on your stay. (raw: Room Rush =?utf-8?b?4oCT?= Enjoy 25% off on your stay.)",
"Last Day To Enjoy Extra 15% OFF On Everything For NDB Credit Cards (raw: =?utf-8?Q?Last=20Day=20To=20Enjoy=20Extra=2015%=20OFF=20On=20Everything=20For=20NDB=20Credit=20Cards?=)",
"Sing Along and Dance with Desmond De Silva at Pegasus Reef Hotel! (raw: =?utf-8?Q?Sing=20Along=20and=20Dance=20with=20Desmond=20De=20Silva=20at=20Pegasus=20Reef=20Hotel=21?=)",
"RE: Weekly Report (CommercialLegal) -\303\202\302\240 2 July 2018 to 5 July 2018 (raw: =?UTF-8?Q?RE:_Weekly_Report_=28CommercialLeg?=\t=?UTF-8?Q?al=29_-=C2=A0_2_July_2018_to_5_July_201?=\t=)",
"How are you",
"=?GB18030?B?XXXXXXXXXX?=");

for my $subj (@subject) {
    my $subject_decoded = decode("MIME-Header", $subj);
    print $subject_decoded;
    print "\n";
}