Present subjunctive with synonyms of lest

Historically, many subordinating conjunctions once triggered “modally marked” forms; that is, those other than the normal indicative. Lest is just one of these; ere, for fear (that), provided (that), and in case are a few more. There are others, but all are rare.

In his play The New Inn, or The Light Heart, Ben Jonson wrote in act 4, scene 3:

She is some giantess: I will stand off, For fear she swallow me.

But as we near the quincentennial of that play’s publication, we read such things with ever decreasing frequency, and hear them even more seldom.

Unlike lest, which still sees occasional use, ere is completely absent in Present-Day English.

Of the others, you do still (very) occasionally read things like in case it were and for fear it were or provided it were. Notice those are all using were not be, triggering a hypothetical, “unreal” understanding, what some would call a past subjunctive. For the present, one would normally use an explicit modal verb like should or might.

Only in writing that is deliberately formal to the point of being archaizing do you find such forms these days. One example appears in Pippin’s oath to Denethor in The Lord of the Rings:

Here do I swear fealty and service to Gondor, and to the Lord and Steward of the realm, to speak and to be silent, to do and to let be, to come and to go, in need or plenty, in peace or war, in living or dying, from this hour henceforth, until my lord release me, or death take me, or the world end.

The wording in Pippin’s oath still sounds right for the high and solemn context in which it occurs. Perhaps this is because we still remember the high-sounding echoes of such solemn oaths: it’s the same construction as we hear in the ancient wedding vow that begins with “I take thee...” and which ends with “...till death do us part”.

Outside of deliberately archaizing language such as that employed by the Steward of Gondor and his interlocutors, you would not normally come across forms like these in today’s writings.

Another set that can trigger a non-indicative verb, this set now less rare than the earlier one just mentioned, includes subordinate clauses governed by subordinating conjunctions like though, although, even if, as if. For example, Job 13:15 runs like this in the KJV:

Though he slay me, yet will I trust in him: but I will maintain mine own ways before him.

That’s another example, but as you will have likely gathered from the occurrence of mine own, no modern translation ever sounds like that one from so long ago.

For more uses of the modally marked form in temporal clauses like these, see Volume II of Visser’s An Historical Syntax of the English Language, in which he treats with all these peculiarities at breathtaking length and detail.