<?php
$subject = "RX3!Pl6HxTCD";
if (substr($subject, 0, 2) === 'RX' && substr($subject, -2) === 'CD') { echo "$subject\n";
}
PD9waHAKCiRzdWJqZWN0ID0gIlJYMyFQbDZIeFRDRCI7CmlmIChzdWJzdHIoJHN1YmplY3QsIDAsIDIpID09PSAnUlgnICYmIHN1YnN0cigkc3ViamVjdCwgLTIpID09PSAnQ0QnKSB7CiAgICBlY2hvICIkc3ViamVjdFxuIjsKfQ==