The example devd entry in the carp(4) man page doesn't handle if you are dealing with a VLAN.  

This is the extract from the existing man page relating to carp.  

---> CUT HERE <---
           notify 0 {
                   match "system"          "CARP";
                   match "subsystem"       "[0-9]+@[0-9a-z]+";
                   match "type"            "(MASTER|BACKUP)";
                   action "/root/carpcontrol.sh $subsystem $type";
           };
---> END CUT <---

Here is a slightly *corrected* entry which handles VLANs.  

---> CUT HERE <---
           notify 0 {
                   match "system"          "CARP";
                   match "subsystem"       "[0-9]+@[0-9a-z\.]+";
                   match "type"            "(MASTER|BACKUP)";
                   action "/root/carpcontrol.sh $subsystem $type";
           };
---> END CUT <---

This handles when there is an subsystem attached to a VLAN (by allowing the "." character in the class).  For example:
   3@em0.1030
or
   2@lagg0.1050