#!/usr/local/bin/perl
use strict;
use warnings;

my %seen = ();
my $string = "an apple a day";
while ($string =~ /(.)/g){
   $seen{$1}++;
}
print "unique charts are:", sort(keys %seen), "\n";

my $sum = 0;
foreach my $ascval(unpack("C*", $string)){
   $sum += $ascval;
}
print "sum is $sum\n";

my $checksum = 0;
while(<>){ $checksum += unpack("%16C*", $_ ) } 
$checksum %= (2 ** 16) -1;
print "$checksum\n";