use strict;
use warnings;
use Data::Dumper;
use IO::String;
use Text::CSV;

my $file1 = IO::String->new(<<EOF) or die "$!";
username, date_modified
2010-nhw-es-ea-285, 2012-10-10
aab.external.audit.-.bvr.verif.externes, 2012-02-22
aashee.aziz, 2012-01-27
abbas.rangwala, 2012-01-27
abbie.gardner, 2012-09-10
ab.border-frontiere, 2012-08-11
abdool.yasseen, 2012-01-31
abdullah.aboukarr, 2012-08-10
abdullahi.sheikh, 2012-02-28 
EOF

my $file2 = IO::String->new(<<EOF) or die "$!";
fullname, branch
aaron.northway, CHIEF FINANCIAL OFFICER BRANCH
aashee.aziz, HEALTH PRODUCTS AND FOOD BRANCH
abbey.klugerman, HEALTHY ENVIRONMENTS AND CONSUMER SAFETY BRANCH
abby.hoffman, STRATEGIC POLICY BRANCH
abderrahim.boussanni, CHIEF FINANCIAL OFFICER BRANCH
abdiaziz.nur, HEALTHY ENVIRONMENTS AND CONSUMER SAFETY BRANCH
abdool.yassin, HEALTH PRODUCTS AND FOOD BRANCH
abdoulie.manjang, N/A
abdullah.hassen, HEALTH PRODUCTS AND FOOD BRANCH
abdullah.patel, REGIONS AND PROGRAMS BRANCH
asdf "asdf" asdf,,
EOF


my $csv1 = Text::CSV->new({
    binary  => 1,
    allow_whitespace    => 1,
    sep_char    => ',',
});

my %date_modified_by_username;
$csv1->column_names( $csv1->getline($file1) );   # get header line
while(my $href = $csv1->getline_hr($file1)) {
    $date_modified_by_username{$href->{username}} = $href->{date_modified};
}


my $csv2 = Text::CSV->new({
    binary  => 1,
    allow_whitespace    => 1,
    sep_char    => ',',
    eol => "\n",
});

$csv2->print(\*STDOUT, [ qw{username branch date_modified} ]);

$csv2->column_names( $csv2->getline($file2) ); # get header line
while(my $href = $csv2->getline_hr($file2)) {
    my $date_modified = $date_modified_by_username{$href->{fullname}}
        || 'unknown';
    
    $csv2->print(\*STDOUT, [
        $href->{fullname}, $href->{branch}, $date_modified
    ]);
}