sub test_loop_1{
    ########   RAM used: 190 MB
    my(@all, $elements);

    @all = ();

    open(FILE, $file) or die;
    while(<FILE>){
       push @all, /\d/og;
    }
    close(FILE);

    $elements = @all;
    print $elements;  # Just for confirmation - prints 2387250
}

sub test_loop_2{
    ########   RAM used: 185 MB
    my(@all, @all2, $all, $elements);
    
    open(FILE, $file) or die;
    @all = <FILE>;
    close(FILE);
    
    $all = join('', @all);
    @all2 = split('', $all);
    $elements = 0;
     
    foreach(@all2){
       $elements ++;
    }

    print $elements;  # Just for confirmation - prints 2387250
}

sub test_loop_3{
    ########    RAM used: 120 MB
    my(@all, @all2, $all, $elements);

    open(FILE, $file) or die;
    @all = <FILE>;
    close(FILE);

    $all = join('', @all);
    @all2 = ();

    for($i = 1; $i <= length($all); $i ++){ 
      push @all2, substr($all, $i, 1);
    }
   
    $elements = @all2;
    print $elements;  # Just for confirmation - prints 2387250
}