#!/usr/bin/perl -w
use strict;

my $string = 'Tom.Dog.Ben.Cat.Howie.Dog.Trigger.Horse';
my @pairs = split(/\./,$string);

my %petNames;                #one way with a hash table
my @twoD_array_simple;       #a simple 2D array
my @twoD_array;              #Another "2-D" way

while (@pairs)
{
   my ($name, $animal) = splice(@pairs,0,2);
   push (@{$petNames{$animal}}, $name);  #one way with a hash table
   push (@twoD_array_simple, [$name, $animal]); #a simple 2D array
   push (@twoD_array, 
         {name => $name, animal => $animal}); #Another "2-D" way   
}

print "A hash table to combine names for each animal:\n";
foreach my $animal (keys %petNames)
{
   print "$animal => @{$petNames{$animal}}\n";
}

print "\nA simple 2-Dimensional array representation:\n";
foreach my $aref (@twoD_array_simple)
{
   print "@$aref\n";
}

print "\nOne item of simple 2-D array (3rd row, second column):\n";
print "$twoD_array_simple[2][1]  ...  that's Howie's animal\n";

print "\nAnother 2-D way without using indices for the columns:\n";
foreach my $href (@twoD_array)
{
   print "$href->{name} is a $href->{animal}\n";
}

print "\nOutput one row using the \"another 2-D way\"\n";
print "$twoD_array[2]->{name} $twoD_array[2]->{animal}".
      " ....that is the third row\n";
 

__END__
PRINTS:

A hash table to combine names for each animal:
Horse => Trigger
Cat => Ben
Dog => Tom Howie

A simple 2-Dimensional array representation:
Tom Dog
Ben Cat
Howie Dog
Trigger Horse

One item of simple 2-D array (3rd row, second column):
Dog  ...  that's Howie's animal

Another 2-D way without using indices for the columns:
Tom is a Dog
Ben is a Cat
Howie is a Dog
Trigger is a Horse

Output one row using the "another 2-D way"
Howie Dog ....that is the third row