#! perl
use strict;
use warnings;
use Data::Dump;
use Text::CSV_XS qw( csv );

my $aoa = csv(in => \*DATA);

my %employees;

# Make an employee => group hash

for my $record (@$aoa)
{
    $employees{ $record->[0] } = $record->[1];
}

# Fill in the missing groups

for my $record (@$aoa)
{
    $record->[1] = $employees{ $record->[2] } if $record->[1] eq '';
}

dd $aoa;

__DATA__
Sam Malone,Cheers,Rebecca Howe
Woody Boyd,,Rebecca Howe
Rebecca Howe,Cheers,Rebecca's Manager

##</code><code>##

 2:46 >perl 1057_SoPW.pl
[
  ["Sam Malone", "Cheers", "Rebecca Howe"],
  ["Woody Boyd", "Cheers", "Rebecca Howe"],
  ["Rebecca Howe", "Cheers", "Rebecca's Manager"],
]

 2:47 >