my %session_hash;
my %departments;
# for each of the 6 session files,
#     open and read line-by-line
#         parse out user_id, session_id, dept_code
          $session_hash{$session_id} = $dept_code;
          $departments{$dept_code}++;
#
# for each apache log
#     open and read line-by-line
#         parse out session_id
#         append the line to the file associated with $session_hash{$session_id}