#!/usr/bin/perl
# The Missing Textutils, Ondrej Bojar, obo@cuni.cz
# http://www.cuni.cz/~obo/textutils
#
# 'insert_every' processes stdin to stdout, writing ARG1 after every n
# lines
#
# $Id: insert_every,v 1.1 2006/09/15 15:26:00 bojar Exp $
#

use strict;
use Getopt::Long;

sub usage {
  print STDERR "insert_every text_to_insert <stdin >stdout
Options:
  --n=X   ... insert after n lines
";
  exit 1;
}

my $n = 10;
my $usage = 0;
GetOptions(
  "help" => \$usage,
  "n=i" => \$n,
);
usage() if $usage;

my $extra = shift;

my $nr = 0;
while (<>) {
  $nr++;
  print;
  print $extra."\n" if $nr % $n == 0;
}