Register (register or r)

import type { Entrypoint } from "https://deno.land/x/denops_std@v6.5.0/mod.ts";
import { register } from "https://deno.land/x/denops_std@v6.5.0/variable/mod.ts";

export const main: Entrypoint = async (denops) => {
  // Set register
  await register.set(denops, "a", "world");

  // Get register
  console.log(await register.get(denops, "a"));
}

Note that register.get() returns defaultValue when the register is falsy.