use warnings;

my %data_sets;

while(<>){
   # I did the $line thing because there's some garbage at the top of the file that I don't want
   my $line++;
   if($line == 2){
      while(/\G([^\t]+)/g){
         $data_sets{$_} = {};
      }
   }
   if($line > 3){
      $data_sets{}; #<- ran into the problem right here! The script doesn't know what data set its on!
   }