Manual:$wgHTCPRouting

Details
Routing configuration for HTCP multicast purging.

Add elements here to enable HTCP and determine which purges are sent where. If set to an empty array, HTCP is disabled.

Each key in this array is a regular expression to match against the purged URL, or an empty string to match all URLs. The purged URL is matched against the regexes in the order specified, and the first rule whose regex matches is used.

Example
Example configuration to send purges for upload.wikimedia.org to one multicast group and all other purges to another: