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

my %books = (
 fred    => 3,
 wilma   => 1,
 barney  => 0,
 pebbles => undef
);

my $someone = 'wilma';

if ($books{$someone}) {
 # Let's fancy it up: show how many books they have!
 print "$someone has $books{$someone} books checked out\n";
}