# pring http header

# decode params

# if required params are not present
#    print explanation with link to sign-up page
#    exit

# open database file for r/w access
# get lock on that file
# read current contents

# if userid from form exists in database
#    close file
#    print explanation with link to sign-up page
#    exit

# print new entry fields to database file
# close file
# print confirmation message