use bigint;
my @array = unpack( "C16", pack( "Q<2", 0xfffefdfcfbfaf9f8f7f6f5f4f3f2f1f0 ) );
print( join( ", ", @array ), "\n" ); # 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 0, 0, 0, 0, 0, 0