SID for previous working page

SID for previous working page

I think its a beginner question but bare with me.
I want to make an authentication model using perl on server side and the
javascript on the client side:
First requirement is to authenticate the username and password. For this i
have created the login page and it prompts the user to input username and
password and then the password is converted to hashed value and then send
to the server where it is matched with the stored hashed password bingooo
it works...
The second requirement is to maintain the state.. i.e if user comes again
then it must go back to the previous page (index) where he was working.
For this my arqument is i can use a file to store the location of the user
at server whenever the user revisits the site he is redirected to previous
page he was working at.
The third requirement is that that specific users are allowed a collection
of pages e.g 10 to 30 which i can do from checking the user url and telly
with the limit of page in the user.txt file
But the project manager told me to use session ids stuff to remember the
previous state... i tried but not understood how it may help my scenerio .
Precious comments are required..