use Benchmark;

for $SIZE (100, 1000, 10000) {

timethese(-5, {
  sp_fr_pu => sub {
    my @a = (1..$SIZE);
    my @b;
    while (my @c = splice(@a, 0, 4)) { push @b, { @c } }
  },
  sp_bk_un => sub {
    my @a = (1..$SIZE);
    my @b;
    while (@a and my @c = splice(@a, -4)) { unshift @b, { @c } }
  },
  sp_bk_in => sub {
    my @a = (1..$SIZE);
    my @b;
    $#b = int(@a / 4);
    my $i = $#b;
    while (@a and my @c = splice(@a, -4)) { $b[$i--] = { @c } }
  },
  in_fr_pu => sub {
    my @a = (1..$SIZE);
    my @b;
    my $i = 0;
    while ($i < @a) { push @b, { @a[$i .. $i + 3] }; $i += 4; }
  },
  sh_fr_pu => sub {
    my @a = (1..$SIZE);
    my @b;
    while (@a) { push @b, { map shift(@a), 1..4 } }
  },
  sp_bk_rv => sub {
    my @a = (1..$SIZE);
    my @b;
    while (@a and my @c = splice(@a, -4)) { push @b, { @c } }
    @b = reverse @b;
  },
});

}