#include <stdio.h>

#ifdef DEBUG
  some code here
#ifdef SOLARIS
  solaris-specific code here
#endif /* SOLARIS */
  this is still debug code
#endif DEBUG
  this is normal code

##</code><code>##

  my $state = 0;
  my $debug = 0;;

  while(<>) {
    $debug=1,$state++,next if /^\s*#if.*DEBUG/;
    $state++ if /^\s*#if/;
    $state-- if /^\s*#endif/;
    $debug=0,next if $debug && $state==0;
    print if $debug==0;
  }