I would have thought there was a BASIC bundle available somewhere. Perhaps try the terms GW-BASIC, QBASIC, PC-BASIC (showing my age
If not, you could try copying and modifying the Batch File
syntax file - it's the nearest equivalent, and quite a small file. There is limited formal structure to it, so it's more or less a question of replacing keywords.
"I'm here to save your life. But if I'm going to do that, I'll need total uninanonynymity." Me Myself & Irene.