{

 #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
}

##</code><code>##

{
    #define mutex 13
  #define inter 14 
 #endif
 #define intel 15
 #define intel_64 16
}

##</code><code>##

{
 #define intel 15
 #define intel_64 16
}

##</code><code>##

my ($start, $stop) = (qr '#ifdef|#if|#ifndef|#else', qr '#endif');

open(file1,$file) or die "Error opening input: " . $!;
open(file2, ">$filea") or die "Error opening input: " . $!;

while (<file1>) {
   if (/$start/ .. /$stop/) {
    next;    
   }
   else
   {
     print file2 $_ ;
   }
}