This is probably the simplest approach:

$/ = 'XXFFDDF';               # set the input record separator
my $base = 'filename';
my $i = 0;
while (<>) {                  # read one section at a time
  my $filename = "$base$i";   # generate a new filename
  open(OUT, ">$filename")     # create and write a new file
    or die "Can't open $filename: $!\n";
  print OUT;
  $i++;
}
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You can generate the filenames however you prefer. I just chose a very simple way of generating the names as an example.

If each section is very long, you might want to read the file in in smaller chunks to conserve memory.

One final note: this puts the XXFFDDF at the end of each file. If you want to put it at the beginning, the code will need to be somewhat different.

You can probably do something like this:

local $/ = "XXFFDDF";   # delimiter

while (<INPUT>) {
   open(OUTPUT, "> output.$.")   # output.1, output.2, etc
      or die "output.$.: $!";   
   print OUTPUT;
   close(OUTPUT);
}
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Hi,
If you want to split one file into lot of files use that pattern as your record separator, that is $/.
Try this one ...

#! /usr/bin/perl -w

my $infil = $0;
my $separator = "XXFFDDF";
local $/ = $separator;

sysopen(INFIL,$infil,O_RDONLY) || die "Can't open $infil: $!.\n";
while(<INFIL>){
  my $out_file = "$infil.$.";
#  s/$separator//;
### if you want to remove your file separator also, uncomment above li
+ne .....
   sysopen(OUT,$file,O_RDWR|O_CREAT|O_EXCL) || die "Can't open for wri
+te tst.$.: $!.\n";
  print OUT $_;
}
close(INFIL);

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There are several ways of accomplishing this task that I can think of. The one best one I can think of in terms of flexibility and efficiency is this (untested code).

my $fil_count = 0;
my $delim = 'XXFFDDF';
open IN, 'in.txt' or die "Can't open in.txt: $!\n";
open OUT, '> out0.txt' or die "Can't write to out0.txt: $!\n";
while (<IN>)
{
  if (/^(.*?)$delim(.*)$/) {
    print OUT $1 if $1;
    close OUT;
    $fil_count++;
    open OUT, '> out' . $fil_count . '.txt' or die "Can't write to out
+${fil_count}.txt: $!\n";
    print OUT $2 if $2;
  }
  else {
    print OUT $_;
  }
}
close IN;
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Coming up with the "best" solution depends a lot on variables like how large the files are, what kind of performance you need, and how you'll come up with the new file name. However, here's the simplest way of solving that (if memory usage and time are no issues).

use strict;
local $/ = undef; # grab everything from file

open FILE, "my_file" or die $!;
foreach $data_block (split /match_instance/, <FILE>) {
    open OUTPUT, "new_file_name" or next;
    print OUTPUT $data_block;
    close OUTPUT;
}
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