use warnings;
use strict;
use diagnostics;

my %bills;
my $currBill = 'void';
my $type = 'header';

$datafile = "datafile.txt";
open(DATA, $datafile) || die ("Cannot open $datafile: $!");

while (<DATA>) {
  chomp;
  if ($_ =~ /^101010000/) {
    $currBill = $1;
    $type = 'header';
  } elsif ($_ =~ /^301033000/) {
    $currBill = $1;
    $type = 'data';
  } else {
    push @{$bills{$currBill}{$type}}, $_;
  }
}
close(DATA);

open($outputdata, '>', 'outputfile.txt' || die "Cannot open output file 

output.txt: $!");

for my $bill (sort keys %bills) {
    print $outputdata ">>>> $bill\n";
    print $outputdata "Header\n" . (join "\n", @{$bills{$bill}{'header'}}) 

. "\n"
        if exists $bills{$bill}{'header'};
    print $outputdata "Data\n" . (join "\n", @{$bills{$bill}{'data'}}) . 

"\n"
        if exists $bills{$bill}{'data'};
}