R function for obtaining a reference to a variable

In Advanced R, environments are advertised as a useful way to get pass-by-reference semantics in R: instead of passing a list, which gets copied, I can pass an environment, which is not. This is useful to know.

But it assumes that whoever is calling my function is happy to agree on an "environment"-based data type, with named slots corresponding to the variables we want to modify.

Hasn't someone made a class which allows me to just refer to a single variable by reference? For example,

v = 1:5
r <- ref(v)
(function() {
    getRef(r)       # same as v
    setRef(r, 1:6)  # same as v <<- 1:6, in this case
})()

It would seem to be pretty easy to do this, by storing the character name of v together with the environment where it is bound.

Is there a standard library which accomplishes this semantics, or can someone provide a short snippet of code? (I haven't finished reading "Advanced R"; apologies if this is covered later in the book)