Assembling documentation in a loop

General Usage
1

I would like to assemble a string that consists of the docstrings of several functions. Here is essentially what I am trying:

"""the function foo | it's fine"""
foo() = nothing

"""another function bar | it's great"""
bar() = nothing

totaldoc = ""
for f in (foo, bar)
    docstring = @doc $f

    global totaldoc *= string(docstring)
end

Running exactly the above returns:

julia> println(totaldoc)
No documentation found.

Binding `f` does not exist.
No documentation found.

Binding `f` does not exist.

Running with @eval @doc $f also does not work

Any ideas on how to get this to work? The reason I am trying this is that for my particular application, it would be very useful to have a function which would list all of the functions available in the module as well as a few words about each one.