#!/usr/bin/perl -w

use strict;

my @hosts = qw(localhost);

HOST:
foreach my $host (@hosts )
{
   open(NMAP, "nmap -O $host |") || next;

   while(<NMAP>)
   {
      chomp;
      if(/Remote operating system guess: (.*)/)
      {
         print "$host $1\n";
         next HOST;
      }
   }
}