The optative is a very good example of the way in which different tenses of the subjunctive convey different meanings
Utinam veniat! │ If only he would come i.e. the speaker is referring to a hope for the future
Utinam venīret! │ If only he were coming (now) i.e. a wish for something to happen in the present
Utinam vēnisset! │ If only he had come; in grammar, this can be called contrary-to-fact i.e. what is wished for can no longer happen
