#!/usr/bin/perl

use warnings;
use strict;

my $depth;
while (<DATA>) {
    /#ifdef|#if|#ifndef/ and $depth++;
    print unless $depth;
    /#endif/ and $depth--; # this comes after the print not to be printed
}


__DATA__
{

 #if 1
  #define done 9
  #define do 10
  #ifdef
    #define def1 11
    #define thread 12
  #endif
  #define mutex 13
  #define inter 14 
 #endif
 #define intel 15
 #define intel_64 16
}