Method #1 

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

use strict;
use warnings;
use DBI;

  my $datafolder = "F:/Perl_program";
  my $dbh = DBI->connect(
     "dbi:CSV:f_dir=$datafolder;f_ext=.csv;csv_eol=\n;"
     );
		
    $dbh->{'csv_tables'}->{"HCDir2.csv"} = {'col_names' => ["fullname", "branch"]};
    $dbh->{'csv_tables'}->{"final2.csv"} = {'col_names' => ["username", "date_modified"]};
			
    $dbh->do("
      CREATE TABLE completed.csv
      AS SELECT final.username,HCDir.branch,final.date_modified
      FROM  HCDir
      INNER JOIN final
      ON final.username = HCDir.fullname
     ");