#!/usr/local/bin/perl -w

my $data = "";
for (0..255) { $data .= chr($_); }  ## All possible byte combinations
open ( my $out, ">", "./testdata" ) or die "$!\n";
my $hdata = unpack("H*",$data);
print $out "$hdata\n";
close $out;

open ( my $in, "<", "./testdata" ) or die "$!\n";

my $sz = read( $in, my $new, 256 );
chomp( $new );
close $in;

my $ndata = pack("H*",$new);
# print "$hdata\n\n$new\n\n"; 

if ( $ndata eq $data ) { print "1. Okay\n"; }
if ( $hdata eq $new ) { print "2. Okay\n"; }
exit;

1;

##</code><code>##

  my $S16bits = substr($new, 0, 4, "" );   ## 4 bytes printable hex

     or

  my $S16bits = substr($ndata, 0, 2, "" );   ## 2 bytes hex data