Index: lib/Catalyst/Plugin/Session/State/Cookie.pm
===================================================================
--- lib/Catalyst/Plugin/Session/State/Cookie.pm	(revision 10480)
+++ lib/Catalyst/Plugin/Session/State/Cookie.pm	(working copy)
@@ -7,7 +7,7 @@
 use MRO::Compat;
 use Catalyst::Utils ();
 
-our $VERSION = "0.11";
+our $VERSION = "0.12";
 
 BEGIN { __PACKAGE__->mk_accessors(qw/_deleted_session_id/) }
 
@@ -61,9 +61,10 @@
     my ( $c, $sid, %attrs ) = @_;
 
     my $cfg    = $c->config->{session};
+    my $cookie_domain = ( ! $cfg->{cookie_domain} ) ? undef : ( ref $cfg->{cookie_domain} eq 'CODE' ) ? $cfg->{cookie_domain}->($c) : $cfg->{cookie_domain};
     my $cookie = {
         value => $sid,
-        ( $cfg->{cookie_domain} ? ( domain => $cfg->{cookie_domain} ) : () ),
+        ( $cookie_domain ? ( domain => $cookie_domain ) : () ),
         ( $cfg->{cookie_path} ? ( path => $cfg->{cookie_path} ) : () ),
         %attrs,
     };
@@ -220,6 +221,17 @@
 
 The name of the domain to store in the cookie (defaults to current host)
 
+or more configurable:
+
+    __PACKAGE__->config->{session}->{cookie_domain} = sub {
+        my $c = shift;
+        if ( $c->req->uri->host =~ /xxx\.com/ ) {
+            return '.xxx.com';
+        } else {
+            return '.yyy.com';
+        }
+    };
+
 =item cookie_expires
 
 Number of seconds from now you want to elapse before cookie will expire.