Example 17-2. Example:
unlock g  | 
unlock_statement ==>
        unlock expression | 
Locks may also be unlocked before exiting the lock branch by an unlock statement. An unlock statement must be syntactically within a lock branch; in a par or fork statement an unlock must be inside an enclosed lock branch. It is a fatal error if the expression does not evaluate to a $LOCK object which is locked by the enclosing lock statement.