use Encode;
my $header = '=?UTF8?B?5LuO5Y2a5a6i5paH56ug5Lit5p+l5om+5oKo5oSf5YW06Laj55qE5Li7?==?UTF-8?B?6aKY?=';
my $utf8   = decode('MIME-Header', $header);
print "uft8: $utf8\n";