MS Teams menus use 'dial patterns' to match the dialed numbers. These patterns use regular expression (regex) strings to check for matches to the dialed digits. For example, the regex string ^2\d{2}$ matches any three-digit number beginning with a 2.
In Dial plans, MS Teams uses these to match numbers dialed by a user and apply to number translations.
In Voice routes, MS Teams uses these to match the number on outgoing calls to routes for the call.