#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11136191
use warnings;

my @test = map 2 * 10 ** $_, 0 .. 16;
for my $n ( 0, @test, map -$_, @test )
  {
  my @bytes = reverse sprintf('%016X', $n) =~
    s/^0{8}(0{4}(00)?)?(?=[0-7])//r =~
    s/^F{8}(F{4}(FF)?)?(?=[89A-F])//r =~
    /../g;
  print "$n => @bytes\n";
  }