ver­sions – Op­tion­ally omit pieces of text

Stephan Bel­lan­toni’s ver­sion has pro­vided pream­ble com­mands for se­lect­ing en­vi­ron­ments to be in­cluded/ex­cluded. This pack­age does the same, but cor­rects, im­proves, and ex­tends it in both im­ple­men­ta­tion and func­tion.