S. + V. + lest that you (should) + V.R.

=S. + V. + for fear that you (should)/(may) + V.R.

舉例：

政府要求民眾保持社交距離，以免人群群聚造成感染。

The government ordered everyone to practice social distancing lest that people (should) get infected due to cluster spreading.

= The government ordered everyone to practice social distancing for fear that people (should)/(may) get infected due to cluster spreading.