#!/usr/bin/env perl

use Data::Dumper;

my @a1 = (undef, 'second');
my @a2;
@a2[1] = 'second';

print Dumper(\@a1, \@a2);
__END__
Outputs:
$VAR1 = [
          undef,
          'second'
        ];
$VAR2 = [
          undef,
          'second'
        ];