How do I use vim registers?

Question

I only know of one instance using registers is via CtrlR* whereby I paste text from a clipboard.

What are other uses of registers?

Answer 1

I think the secret guru register is the expression = register. It can be used for creative mappings.

:inoremap  \d The current date =system("date")

You can use it in conjunction with your system as above or get responses from custom VimL functions etc.

or just ad hoc stuff like

=35+7