It should be possible to use two different barcodes, to detect the difference between the door opening and the door closing (based on the order of the scans within a short interval) so you could list the current status (open or closed).

As to the code at hand ... why use open(TIME,"date|"); instead of localtime ?

You might also want to change it so it updates a data file with the value of i ... that way if the script dies for any reason, you still know the total.