Manual:$wgAutopromote

Details
This array contains criteria of automatic promotion. The syntax is:

  here may be:

A Autopromote>Special:MyLanguage/Manual:$wgAutopromote#Set of conditions|set of conditions
 * A single condition

Possible conditions
Possible conditions (defined in ; extensions may add more through the  hook):

Conditions with and without arguments
Each condition can be written in two forms:

Set of conditions
Sets of conditions have the following syntax:

There are 4 operands available:

promote if user matches all conditions promote if user matches any condition promote if user matches only one of two conditions &mdash; promote if user matches no conditions.
 * & (AND) —
 * | (OR) —
 * ^ (XOR) —
 * ! (NOT)

The sets of conditions are evaluated recursively, so you can use nested sets of conditions linked by operands.

Caveats
Autopromotion doesn't actually add users to a group; MediaWiki will check whether a user meets the conditions for autopromotion whenever it checks the user's rights or effective groups. This means that a user will only appear to be in a group on Special:ListUsers if they were added to it through Special:UserRights. It also means you can't directly remove a user from an autopromotion group through Special:UserRights: RevokePermissions>Special:MyLanguage/Manual:$wgRevokePermissions|$wgRevokePermissions might be useful for you, or if you're not using MediaWiki 1.16+,  is available.

Example
If you wanted to autopromote each user to captain upon his having both confirmed his email address and either made at least 100 edits or registered his account at least 60 seconds ago, you would use:

Note that this would get rid of all other autopromote groups; to instead add the captain autopromote group while keeping those autopromote groups that already exist, one would use: