gistfile1.pl

use strict;
use warnings;
use feature ":5.10";

my @ar = qw( a b c d );
my $ar_ref = \@ar;

say @ar;      # abcd
say @$ar_ref; # abcd - same array, so same contents

# $#ar is the index of the last element in @ar
say $#ar;        # 3
say $#$ar_ref;   # 3 - same array, same index

say $#($ar_ref); # warning!