MCBlockBreakEvent

The event is cancelable.

If the event is canceled, prevents the block from being broken.

The event does not have a result.

It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import at the very top of the file.

import crafttweaker.api.event.block.MCBlockBreakEvent;

MCBlockBreakEvent extends MCBlockEvent. That means all methods available in MCBlockEvent are also available in MCBlockBreakEvent

MCBlockBreakEvent.getExpToDrop() as int
myMCBlockBreakEvent.getExpToDrop();

MCBlockBreakEvent.getPlayer() as MCPlayerEntity
myMCBlockBreakEvent.getPlayer();

MCBlockBreakEvent.setExpToDrop(amount as int) as void