Assuming that your data file always begins with a matching pattern on the first line as in the sample data you provided, the following would work. 

use strict;
use warnings;

while(<DATA>){
  if(/DN:$/){
    chomp(my $filename = <DATA>);
    open FH, '>', $filename or die;
  }
  else { print FH $_; }
}

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In reply to Re: Split file by arun_kom
in thread Split file by Anonymous Monk

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