#if 0
  this shouldn't print
  #if 1
     nor should this
  #else
     nor this
  #end
#else
  but this should
  #if 1
     as should this
  #else
     but not this
  #end
  This should print, but where are you storing the information
  to know it without a stack?
#else
  If you got that one right, howzabout this one?
#end