print(var_1)
print("world")
print(var_2)

print("hello")
print("world")
print("goodbye")

esubstitute <- function(expr, envir) do.call("substitute", list(expr, envir))

do_something <- function(todo, envir = parent.frame()) {
  cat(
    paste(
      deparse(esubstitute(todo, envir)),
      collapse = "n"
    )
  )
}

nested_do <- function(envir = parent.frame()) {

  var_2 <- "goodbye"

  do_something({
    print(var_1)
    print("world")
    print(var_2)
  }, envir)

}

var_1 <- "hello"

nested_do()

[1] "hello"
[1] "world"
[1] "goodbye"
"goodbye">