my %database;
my $curCol;
for(<DATASET>)
{
  if(/^(col\d+)\s+(.*)/)  #(.+) isnt good but as I dont know exactlly how your data looks like...
  {
    push(@{$database{$1}}, $2);
    $curCol = $1;
  }
  elsif(/^\s+(.*)/)
  {
    push(@{$database{$curCol}}, $1);
  }
}