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

my $hr_file = 'HR.txt';
open my $fh, '<', $hr_file or die $!;

my (undef, @hdr_hr) = split /,/, <$fh>;
chomp @hdr_hr;

my %hr_data;
while (<$fh>) {
    chomp;
    my ($id, @rest) = split /,/;
    @{ $hr_data{$id} }{@hdr_hr} = @rest;
}
close $fh or die $!;

my $ad_file = 'AD.txt';
open $fh, '<', $ad_file or die $!;

my (undef, @hdr_ad) = split /,/, <$fh>;
chomp @hdr_ad;

@hdr_ad ~~ @hdr_hr or die "Uncompatible headers between HR and AD files\n";

my %ad_data;
while (<$fh>) {
    chomp;
    my ($id, @rest) = split /,/;
    @{ $ad_data{$id} }{@hdr_ad} = @rest;
}
close $fh or die $!;

for my $id (sort keys %hr_data) {
    next unless exists $ad_data{$id};
    for my $hdr (@hdr_hr) {
        my $description_hr = $hr_data{$id}{$hdr};
        my $description_ad = $ad_data{$id}{$hdr};
        print "$id,$hdr,$description_hr\n"
            unless $description_hr eq $description_ad;
    }
}