PL research and reverse engineering or just fixing compatibility. Say you want a program from 3.6 era but the 107 year old interpreter doesn't quite suit you an

PL research and reverse engineering or just fixing compatibility. Say you want a program from 3.6 era but the 107 year old interpreter doesn't quite suit you and the newest one broke something, and you bisect interpreter versions to find 3.11 to 3.12 broke it.