What happens if you just start using the hash without initializing it? Most of the time, Perl does the right thing without complaint. If you add to a element that does not exists, Perl pretends it's zero and adds the number. If you push on a non-existent array, Perl creates it and pushes the value.

But if you insist on initializing the hash, use a simple loop:

#!/usr/bin/perl

use strict;
use warnings;

my %hash = ();
my $length = 10;

for my $index ( 0 .. $length-1 ){
  $hash{COUNTS}[$index] = 0;
  $hash{LISTS}[$index] = [];
}

print '%hash ', Dumper \%hash;
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