OK, I've cleared the list of new iRule features in 9.4.2. This is mostly just an overview of them, I'm not going to attempt to really document them here. More complete info should appear in the Wiki over the next few months. Here's the list:
New events:
*) PERSIST_DOWN (fires when a persistence entry would send a request to a down node)
*) CACHE_UPDATE (fires when a cache entry is updated, presumably)
*) SIP_RESPONSE_SEND (analogous to the HTTP_REQUEST_SEND event, I think)
New commands:
*) Many SCTP:: commands (already in the Wiki)
*) SIP::payload command (for accessing the SIP payload, ala TCP::payload)
*) CACHE::fresh (Returns true or false, indicating if the document is fresh (is cached and not stale))
*) CACHE::statskey (Sets the stats bucket for the cached document, to provide statistics in user-defined groups)
*) CACHE::header {insert, value, remove, replace, exists} commands (analogous to the HTTP::header commands, but for cached documents)
Updated commands:
*) active_members (and active_nodes) now take the "-list" parameter, which will return a TCL list of the active members (this is a long-requested feature).
*) matchclass and findclass can now use classes without requiring the "$::" prefix. This is to allow classes on CMP-enabled VIPs. (Without this change, the "$::" prefix would make the BIG-IP system believe a global variable was being referenced, which would disqualify the VIP from running in CMP mode.)
*) HTTP::response now can have the "noserver" keyword after the code parameter. This specifies that the "Server: BIG-IP" header won't be inserted.