#!/usr/bin/env perl
use strict;
use warnings;

my $ar1 = [1,2,3];
my $ar2 = [4,5,6,7];

my @arrays = ($ar1,$ar2);

foreach my $ary (@arrays) {
    # correct syntax
    print $#{@$ary}, "\n";
    # correct length
    print scalar(@$ary), "\n";
}