+* "`user(username)`" - tests whether a modification is being made by a
+ user with the specified username. If openid is enabled, an openid can also
+ be put here.
+* "`admin()`" - tests whether a modification is being made by one of the
+ wiki admins.
+* "`ip(address)`" - tests whether a modification is being made from the
+ specified IP address.
+* Some additional special-purpose limits may be enabled, for matching
+ [[attachments|attachment]] and [[translations|po]].