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%Pet_Food = (
  'dog' => 'dog chow',
...

# $pet_type should be 'dog', 'cat', or 'parakeet'
my $food = $Pet_Food{$pet_type};

@Pet_Types = ("dog", "cat", "dog", "parakeet", "dog", "cat");

...
my @unique_types = sort keys %type_table;
# @unique_types winds up with 'cat', 'dog', and 'parakeet'

%Valid_Pets = (
   'dog' => 1,
...
# but might not.. we die if it doesn't
exists $Valid_Pets{$pet_type}
  or die "I'm sorry, '$pet_type' is not a valid pet\n";

name=fluffy species=rabbit weight=5 price=10.00
name=fido species=dog weight=15 price=30.15
name=gul_ducat species=cat weight=10 price=40.20

while (<PET_FILE>) {
  my %pet = parse_pet($_);
...
  }
  return %params;
}

while (<PET_FILE>) {
  my $pet = parse_pet($_);
...
  }
  return \%params;
}

# Note: Bad code! No krispy kreme!
if ( $pet_type eq 'dog' ) {
...
  print_lemur_page();
}
# .. ad nauseum

%Pet_Pages = (
  dog => \&print_dog_page,
...
my $page_sub = $Pet_Pages{$pet_type}
   or die "Invalid pet type\n";
&$page_sub();