Unlike cash, central bank digital currencies (CBDCs) will be programmable.

says Ravi Menon, former managing director of Singapore's central bank.

"The ownership rights are expressed in digital form, in the form of a program, and so you can write into the program conditions for its use... So it is basically the ability to write a computer software program on money, to move it around for a specific purpose."

Can you imagine what kind of usage conditions will be programmed into CBDCs if they're ever allowed to get off the ground?