Variable substitiution in help strings

[Rafael Laboissiere <rafael@xxxxxxxxxx>]

Hi,

Is there a way to get shell variables substituted in help strings of
AC_ARG_WITH?  I mean, with the code below:

    foo=yes
    AC_ARG_WITH(foo, [--with-foo    (default: $foo)])
    
I see:

    $ ./configure --help | grep foo
    --with-foo    (default: $foo)

But I would like to see:

    $ ./configure --help | grep foo
    --with-foo    (default: yes)
                            ^^^

[Please, Cc: replies to me.]

-- 
Rafael