Perl Hello script

#! /usr/bin/env perl

use strict;
use warnings;

print "Hello World!\n";
my $string = "Cloud";
my $number = 9;
my $lil_float = 2e-12;
print '"$string $number": ', "$string $number\n";
print '$lil_float: ', $lil_float, "\n";
print '$lil_float+1: ', $lil_float+1, "\n";
my @books = ( "Pride and Prejudice",
              "Bambi: Eine Lebensgeschichte aus dem Walde",
              "To Kill a Mockingbird",
              "The Adventures of Huckleberry Finn",
              "Oliver Twist",
              "Middlemarch",
              "Le Petit Prince"
            );
my %auth_book = ( 'Austen'  => "Pride and Prejudice",
                  'Salten'  => "Bambi: Eine Lebensgeschichte aus dem Walde",
                  'Lee'     => "To Kill a Mockingbird",
                  'Twain'   => "The Adventures of Huckleberry Finn",
                  'Dickens' => "Oliver Twist",
                  'Eliot'   => "Middlemarch",
                  'Saint Expuery' => "Le Petit Prince"
                );
my $bk_ref_ref = [ \@books, \%auth_book ];
print '@books: ', @books,"\n";
print '%auth_book: ', %auth_book,"\n";
print '"@books": ', "@books\n";
print '"%auth_book": ', "%auth_book\n";
print '"@books[2,3]": ', "@books[2,3]\n";
print '"@auth_book{\'Saint Expuery\', \'Lee\'}": ',
      "@auth_book{'Saint Expuery', 'Lee'}\n";
print '$bk_ref_ref: ', "$bk_ref_ref\n";
print '"@$bk_ref_ref": ', "@$bk_ref_ref\n";
print '"@{@$bk_ref_ref[0]}": ', "@{@$bk_ref_ref[0]}\n";
print '"$bk_ref_ref->[0]->[0]": ', "$bk_ref_ref->[0]->[0]\n";
print '"@{$$bk_ref_ref[1]}{\'Eliot\', \'Twain\'}": ',
      "@{$$bk_ref_ref[1]}{'Eliot','Twain'}\n";