#!/usr/bin/perl -w 
 
use strict; 
 
my $data = join '', <DATA>; 

if($data =~ s|(?=^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\nOS Type: unknown$)|\n|gm)
{
	print "yes, it worked!";
} 
 
#print $data; 
 
exit(1); 
 
__DATA__ 
10.1.1.1 
bogus info 
10.1.1.2 
this could be anything 
10.1.1.3 
OS Type: unknown 
10.1.1.4 
filler information 
10.1.1.5 
OS Type: unknown