1010100.........123456.....   #header line for bill # 123456
#some data
#some data
#some data
#some data
1010100.........678910.....    #header line for  bill # 678910
#some data
#some data
#some data
3010330.........123456.....   #bill detail for bill 123456
#some data
#some data
#some data
#some data
#some data
3010330.........678910.....   #bill detail for bill 678910

For eg. each bill should be split and joined like this:
1010100.........123456.....   #header line for bill # 123456
#some data
#some data
#some data
#some data
3010330.........123456.....   #bill detail for bill 123456
#some data
#some data
#some data
#some data
#some data
<br>

##</code><code>##

#/usr/bin/perl -w
#This script takes a main file and separates into individual bills by splitting at the header line.

#   [-v|--verbose] 
#   [-d|--dest splitdir] filename
#

use Getopt::Long;

GetOptions("verbose" => \$verbose,
           "dest:s" => \$destdir);

if (length $destdir == 0) {
  $split_file_prefix = $ARGV[0];
} else {
  $split_file_prefix = $destdir."/".`basename $ARGV[0]`;
  chomp($split_file_prefix);
}

## open file name passed in as arg 1 for reading
open(MAIN_BATCH_FILE, "<$ARGV[0]") or die "Couldn't open file : 

$ARGV[0] \n Message : $!";

$first_line = <MAIN_BATCH_FILE>;
$counter = 1;
$filename = $split_file_prefix."-SPLIT-".$counter.".txt";
if ($verbose) {
  print "$filename\n";
}

open(NEW_FILE,">".$filename);

print NEW_FILE $first_line;
while (<MAIN_BATCH_FILE>) {

  if ($_ =~ /^1010100/) {
    close(NEW_FILE);
    $counter++;
    $filename = $split_file_prefix."-SPLIT-".$counter.".txt";
    if ($verbose) {
      print "$filename\n";
    }
    open(NEW_FILE,">".$filename);
  }
  print NEW_FILE "$_";
}
close(NEW_FILE);

exit 0;