my ($session_id, $last_action_date, $last_action_time) = split /-/, $session;

##</code><code>##

0 1 2 3 4 5 6 7 8 9

##</code><code>##

# split:
my @fields = split /-/, $session;
die "Weird timestamp in >>$session<<"
    unless @fields == 5;
my ($session_id) = $fields[0];
my ($last_action_date) = join "-", @fields[1,2,3];
my ($last_action_time) = $fields[4];

# unpack:
my ($session_id,$last_action_date,$last_action_time) = unpack "A2xA10xA8", $session;

# regex:
$session =~ /^(\d{2})-(\d{4}-\d{2}-\d{2})-(\d\d:\d\d:\d\d)$/
    or die "Weird timestamp in >>$session<<"
my ($session_id,$last_action_date,$last_action_time) = ($1,$2,$3);