use strict;
use warnings;

foreach my $num (2, 20, 200, 2000, 20000, 200000)
{

   my $hex_text = sprintf "%x", $num; #use %X for ABCDEF instead of abcdef
   
   # we are printing bytes, not nibbles, num chars needs to be even
   
   $hex_text = "0$hex_text" if (length($hex_text) % 2 == 1); #add leading 0 if odd
   
   $hex_text =~ s/([0-9a-fA-F][0-9a-fA-F])(?=[0-9a-fA-F])/$1 /g;
   
   my $reversed_bytes = join(" ", reverse split(" ", $hex_text));
   
   print "$num => $reversed_bytes => $hex_text\n";
   
}


__END__
Number => LSB first => MSB first
2 => 02 => 02
20 => 14 => 14
200 => c8 => c8
2000 => d0 07 => 07 d0
20000 => 20 4e => 4e 20
200000 => 40 0d 03 => 03 0d 40

##</code><code>##

2 => 2
20 => 14
200 => c8 00
2000 => d0 07
20000 => 20 4e
200000 => 40 0d 03 00