r - Using substitute in multiple function calls

Question

foo <- function(arg) {
  substitute(arg)
}

foo1 <- function(parm) {
  foo(param)
}
foo1(2 + 2)

output is:

param

How can I use substitute inside foo such that the output will be the expression 2 + 2?

Answer 1

foo1 <- function(parm) {
  p <- substitute(parm)
  do.call(foo, list(p))
}
foo1(2 + 2)
#2 + 2