my @items = qw( loads of variable size items here );
while (@items) {
  push @tapes, remove_from(\@items);
}

sub remove_from {
  my $arrayref = shift;
  my $taperef = [];

  # Knapsack algorithm goes here
  # ...
  
  # Whatever we put in $taperef is removed from $arrayref
  # ...

  return $taperef;
}