use CGI;
my $query = new CGI;
my $user = $justloggedin;

my $newcookie = $query->cookie( 
    -name    => 'arbitrarycookiename',
    -value   => $user,
    -expires => '+15m'); #no activity in 15min...gone!

print $query->header(-cookie => $newcookie); #write it

##</code><code>##

my $user = $query->cookie('arbitrarycookiename'); #read it
if ($user) { $stillloggedin } else { &loggin() }