G'day jzelkowsz,

Here's a solution using Text::CSV (if you have Text::CSV_XS installed it will run faster) and in-memory files (see open). The input data I used is a verbatim copy of what you posted here. 

#!/usr/bin/env perl

use strict;
use warnings;

use Text::CSV;

my ($hr_file, $ad_file, $com_file) = qw{hr.txt ad.txt com.txt};

my (@col_index, %hr_record_for);

my $csv = Text::CSV::->new({quote_space => 0})
    or die "Can't instantiate a Text::CSV object: ",
            Text::CSV::->error_diag();

{
    open my $mem_fh, '<', canonicalise_file_in_memory($hr_file)
        or die "Can't read in-memory file: $!";

    @col_index = @{$csv->getline($mem_fh)};

    while (my $row = $csv->getline($mem_fh)) {
        $hr_record_for{$row->[0]} = $row;
    }
}

{
    open my $mem_fh, '<', canonicalise_file_in_memory($ad_file)
        or die "Can't read in-memory file: $!";
    open my $out_fh, '>', $com_file
        or die "Can't write '$com_file': $!";
    
    (undef) = $csv->getline($mem_fh);

    while (my $row = $csv->getline($mem_fh)) {
        for my $i (1 .. $#col_index) {
            if ($hr_record_for{$row->[0]}[$i] ne $row->[$i]) {
                $csv->say($out_fh, [
                    $row->[0], $col_index[$i],
                    $hr_record_for{$row->[0]}[$i]
                ]);
            }
        }
    }
}

sub canonicalise_file_in_memory {
    my ($file) = @_;

    open my $fh, '<', $file or die "Can't read '$file': $!";

    my $canon;

    while (<$fh>) {
        chomp if /,$/;
        $canon .= $_;
    }

    return \$canon;
}

[download]

Output:

$ cat com.txt
barsu991,mail,Uttiam.Barski@pulse.org
barsu991,title,Director of Cooks
walkl003,givenname,Lreblemet
walkl003,employeenumber,20178941
walkl003,mail,Lreblemet.Walker@pulse.org
walkl003,title,Head Cook
karss001,givenname,Sovyetk
karss001,mail,Sovyetk.Karsten@pulse.org
karss001,title,Dishwasher
karss001,physicaldeliveryoffice,Kitchen of the World
karss001,streetaddress,205 Willy B. Temple
karss001,st,WI
karss001,postalcode,50987
zingk072,givenname,Kovon
zingk072,employeenumber,20113578
zingk072,symphonyemployeetype,IKP
zingk072,mail,Kovon.Zingerman@pulse.org
zingk072,manager,"cn=manager1,ou=users,ou=Kitchen,dc=Kitchen,dc=net"
hutcy231,givenname,Yello
hutcy231,mail,Yello Hutchinson
haserz221,sn,Haserkrilk
haserz221,employeenumber,20125471
haserz221,mail,Zebediah.Haserkrilk@kit.org
haserz221,telephonenumber,

[download]

— Ken

In reply to Re: Comparing two files line by line and exporting the differences from the first file by kcott
in thread Comparing two files line by line and exporting the differences from the first file by jzelkowsz

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