Here is another way, using JSON to make your storage files

  use strict; use warnings; 
  use JSON; 
  my $usedeltatime=0; 
  eval 'use time::DeltaTime;' if ($usedeltatime);  

  my @bigarray; 
  my %bighash; 


  doit(0,0);
  doit(1,0);
  doit(1,1);

sub doit { 
  my $usecache1=shift; 
  my $usecache2=shift; 

  deltatime('all','set')  if ($usedeltatime); 

if ($usecache2) {$usecache1=1;} 

if ($usecache1){ 
    open (my $cache1,'<','json1.json') or die $@; 
    my $save= do {local $/;<$cache1>}; 
    close $cache1; 
    @bigarray= @{decode_json($save)}; 
    deltatime('all','stage','cache1r:'.$usecache1)  if ($usedeltatime)
+; 
    } 
else {   
    for my $ii (1..30000) { 
      if (rand(100)>80) { push @bigarray,$ii; } 
      } 


    my $save = encode_json (\@bigarray);
    open (my $cache1,'>','json1.json') or die $@; 
    print $cache1 $save; 
    close $cache1; 
    deltatime('all','stage','cache1w:'.$usecache1)  if ($usedeltatime)
+; 
    } 

if ($usecache2){ 
    open (my $cache2,'<','json2.json') or die $@; 
    my $save= do {local $/;<$cache2>}; 
    close $cache2; 
    %bighash= %{decode_json($save)}; 
    deltatime('all','stage','cache2r:'.$usecache2)  if ($usedeltatime)
+; 
    } 
else {   
    foreach my $i (@bigarray){
      foreach my $j (@bigarray) {
        my $positive = $i + $j;

        next if $positive > 28123;

        $bighash{$positive} ++;
        }
      }
    my $save = encode_json (\%bighash);
    open (my $cache2,'>','json2.json') or die $@; 
    print $cache2 $save; 
    close $cache2; 
    deltatime('all','stage','cache2w:'.$usecache2) if ($usedeltatime);
+ 

    }

    print 'array:'.scalar(@bigarray)."\n";; 
    print 'hash :'.scalar(keys %bighash)."\n";; 


    deltatime('all','done','cache1:'.$usecache1.'cache2:'.$usecache2) 
+if ($usedeltatime); 


} # dout
[download]

I have a little routine to create delta-times between stages, you dont, so leave $usedeltatime=0; Others may show you different ways of timing, ive been using deltatime for almost 2 decades, so i used it now.

d-time:000:00:00 000:00:00->all:cache1w:0
d-time:000:00:30 000:00:30->all:cache2w:0
array:5994
hash :28079
d-time:000:00:00 000:00:30->all:cache1:0cache2:0@2017-04-09-04-33-41
d-time:000:00:00 000:00:00->all:cache1r:1
d-time:000:00:29 000:00:29->all:cache2w:0
array:5994
hash :28079
d-time:000:00:00 000:00:29->all:cache1:1cache2:0@2017-04-09-04-34-10
d-time:000:00:00 000:00:00->all:cache1r:1
d-time:000:00:01 000:00:01->all:cache2r:1
array:5994
hash :28079
d-time:000:00:00 000:00:01->all:cache1:1cache2:1@2017-04-09-04-34-11
[download]

With deltatime enabled, no caching used 29 seconds, caching just bigarray used 29 seconds, but caching both bigarray and bighash only used 1 second

YMMV