#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use feature 'say';

my @array;
$array[0] = undef; # Assigns the value 'undef' to $array[0]
$array[3] = 2;
# print Dumper \@array;

for my $value (@array) {
    say "Defined: \$array[$value]" if defined $value;
}

__END__

$ perl test.pl 
Defined: $array[2]