Had I been rich, I __.

Had I been rich, I would have helped the poor.
Conditional sentence এ Had + Sub + V3 + Ext. এভাবে কোন sentence শুরু হলে সেটিও Perfect conditional/ 3rd conditional হয়।
if clause- এ যদি (had + V3) হয়, তবে পরবর্তী clause a would/could/might + have + V3 + extension. ব্যবহৃত হয়।