Challenge 3: exists vs Truthiness — Possible Solution
====================================================================

use strict;
use warnings;
use feature 'say';

my %inventory = ("apples" => 5, "bananas" => 0);

if ($inventory{"bananas"}) {
    say "Truthiness check: bananas present";
} else {
    say "Truthiness check: bananas NOT present";
}

if (exists $inventory{"bananas"}) {
    say "exists check: bananas present";
} else {
    say "exists check: bananas NOT present";
}

Output:
Truthiness check: bananas NOT present
exists check: bananas present

WHY THIS WORKS AS AN ANSWER
------------------------------
if ($inventory{"bananas"}) reuses plain scalar truthiness — in Perl,
0 is a false value, exactly like in most languages. Since
$inventory{"bananas"} IS 0 (a legitimately stored value, not a
missing key), this check evaluates to false, printing "NOT present"
— even though the key genuinely exists in the hash.

if (exists $inventory{"bananas"}) reuses the chapter's own exists
function directly, which the chapter's own warn-box describes as
answering "is this key present at all, independent of whatever value
it happens to hold." Since "bananas" WAS added to %inventory (with
the value 0), exists correctly reports it as present, regardless of
that value being falsy.

One-sentence explanation: the two checks answer genuinely different
questions — plain truthiness asks "is this value truthy" (and 0 isn't),
while exists asks "is this key actually in the hash" (and it is) —
so a key stored with a legitimately falsy value like 0 will always
disagree between the two, exactly the trap the chapter's own
newborn-age example warns about.