Manual:$wgAutopromote

Details
This array contains criterias of automatic promotion. The syntax is: cond here may be: The latter has following syntax: There are 3 operands available: Condition can be written in two forms:
 * A single condition
 * A set of conditions
 * & (AND) — promote if user matches all conditions
 * | (OR) — promote if user matches any condition
 * ^ (XOR) — promote if user matches only one of two conditions