merging environments

   Despite the spirited arguments of various R-core folks
 who feel that mle() doesn't need a "data" argument, and
 that users would be better off learning to deal with function
 closures, I am *still* trying to make such things work
 in a reasonably smooth fashion ...

   Is there a standard idiom for "merging" environments?
 i.e., suppose a function has an environment that I want
 to preserve, but _add_ the contents of a data list --
 would something like this do it? Is there a less ugly
 way?

 x <- 0
 y <- 1
 z <- 2

 f <- function() {
     x+y+z
 }

 f2 <- function(fun,data) {
     L <- ls(pos=environment(fun))
     mapply(assign,names(data),data,
                      MoreArgs=list(envir=environment(fun)))
     print(ls(pos=environment(fun)))
 }

 f2(f,list(a=1))