Method #4

#!F:\Perl_program\perl\bin\perl -w  #I am using Portable Strawberry PERL on Windows XP.

use strict;
use warnings;

our $file1 = "F:/Perl_program/final2.csv";
our $file2 = "F:/Perl_program/HCDir2.csv";
our $fileOut = "F:/Perl_program/completed.csv";

our %file1Map = ();
our %file2Map = ();

open (FILE1, "<final.csv") or die("Could not open $file1 file.");
foreach our $line1 () {
	(our $username, our $date_modified) = split(',',$line1,2);
	our $File1Map{"$username"} = "$date_modified";
}

close(FILE1);

open (INPUT2, "<modhcdir2") or die("Could not open $file2 file.");
foreach $line2() 
{
	(our $fullname,our $branch) = split(',',$line2);
	our $File2Map{"$fullname"}="$branch";
}

close(FILE2);

open (OUTFILE, ">completed.csv") or die("Could not open $fileout file.");
foreach $fileout(){
	(our $username2,our $dumour)=split('\n',$fileout);
	our $existingValue = $File1Map{"$username"};
	our $newValue = $File2Map{"$fullname"};

	if (! defined $existingValue){
		$existingValue = ",";
	}
	if (! defined $newValue){
		$newValue = "\n";
	}

print OUTFILE "" . $username2 . "," . $existingValue . "," . $newValue;
}

close (OUTFILE);