#!/usr/bin/perl -w
use strict;
open(FILE,"file.txt") or die "Cant open file.txt: $!";
1 while <FILE>;
my $line=$.-30;
$.=0;
open(FILE,"file.txt") or die "Cant open file.txt: $!";
open(FILE2,">file2.txt") or die "Cant create file2.txt: $!";
while(<FILE>)
{
	print FILE2 $_;
	insert(*FILE2) if $.==$line;
}
rename("file2.txt","file.txt") or die "Cant rename file: $!";

sub insert
{
	my $fh=shift;
	print "Inserting at line $line\n";
	print $fh "$_\n" for 0 .. 15;
}