$f->add_point('100,199', 900); # 100..199 once every 15 min
  $f->add_point('200,'   ,  60); # 200...   once every minute

  $f->test_point(210);           # returns true
  $f->test_point(211);           # returns false
  sleep(61);                     # wait over 60 seconds
  $f->test_point(211);           # returns true now