#!/usr/bin/perl
use warnings;
use strict;

my %Invoices;

my $last_name = '';
my %data;
while(my $line = <DATA>) {
  chomp $line;
  # Split the fields into a hash.  Depending on your
  # data, this might be better done with Text::xSV.
  @data{qw(orig inv name date time)} = ($line, split(/\s+/, $line));

  next unless $data{name} eq 'Robb' or $data{name} eq 'Larry';
  next if $last_name eq $data{name};

  # If this field passes the tests, save a *copy* for later use.
  push @{$Invoices{$data{name}}}, {%data};

} continue {
  # Store the last name seen
  $last_name = $data{name};
}

# For each (Larry Robb)
foreach (keys %Invoices) {
  # Sort the invoices by date then time, in reverse order.
  $Invoices{$_} = [sort {
    $b->{date} cmp $a->{date} or
    $b->{time} <=> $a->{time}
  } @{$Invoices{$_}}];

  # Print out the most recent invoice.
  print "Most recent for $_: $Invoices{$_}[0]{orig}\n";
}

__DATA__
1056128833340 Robb 2003-06-20 665 **
1056128833340 t028348 2003-06-20 607
1055439973653 T012697 2003-07-22 962
1055439973653 t012697 2003-07-22 948
1055439973653 t806174 2003-07-15 792
1055439973653 T806174 2003-07-15 791
1055439973653 t021191 2003-07-08 786
1055439973653 Robb 2003-06-17 503
1055439973653 Larry 2003-06-16 815 **
1055439973653 t021191 2003-06-12 646