my @sheet = () ;
  while ($line = <SHEET>) {
    my @columns = split /\s+/, $line ;
    push @sheet, \@columns ;
  } ;

##</code><code>##

  my (@sheet, @columns) ;
  while (my $line = <SHEET>) {
    @columns = split /\s+/, $line ;
    push @sheet, \@columns ;
  } ;

##</code><code>##

  push @sheet, [ @columns ] ;

##</code><code>##

  push @sheet, [ split /\s+/, $line ] ;