sub s2 {
  my @r2;
  while (@_) {
    push @r2, [ splice @_, 0, 2 ];
  }
  return \@r2;
}

##</code><code>##

sub s2 {
  my @r2;
  push @r2, [ splice @_, 0, 2 ] while @_;
  return \@r2;
}