use strict;

##</code><code>##

#@internal_array_ref[1] = 20;
# better as
$internal_array_ref[1] = 20;

##</code><code>##

for my $key_primary (keys %internal_hash_ref) {

  print qq{primary key: *$key_primary*\n};

  for my $key_secondary (keys 
%{$internal_hash_ref{$key_primary}}){

    print qq{\tsecondary key: *$key_secondary*\n};
    print qq{\t\t*@{$internal_hash_ref{$key_primary}{$key_secondary}}*\n};

  }

}

##</code><code>##

primary key: *1*
  secondary key: *1_b*
    *34 33 49 32 46 47 27 31 46 30*
  secondary key: *1_a*
    *44 20 20 32 32 47 39 35 24 41*
primary key: *2*
  secondary key: *2_a*
    *34 23 24 30 10 38 47 23 17 25*
  secondary key: *2_b*
    *45 47 44 44 45 39 13 35 14 23*