The built-in template "Template Module Cisco Inventory SNMPv2" has key system.sw.os, which has a regexp preprocessing rule "Version (.+), RELEASE". When this template is assigned to a cisco switch, this results in an error in zabbix_server.log:

Item preprocessing step #1 failed: cannot perform regular expression match on value "Cisco IOS Software, C2960 Software (C2960-LANBASEK9-M), Version 12.2(44)SE6, RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Mon 09-Mar-09 18:10 by gereddy" of type "string": pattern does not match
e.g. grep -P "Version (.+), RELEASE" on the zabbix log file correctly returns the error line so the regular expression seems correct.