[plt-scheme] Using a C/C++ extension in a module

Hi:

I understand that doing (load-extension "x.dll") binds all the variables in 
that extension to the top-level environment. How do I make the same thing 
happen in a module? That is, I want to use an extension, but to confine its 
bindings only to within that module. This doesn't work.

(module mymodule mzscheme
    (load-extension "x.dll")
    (provide a b c) ; These are the variables defined in the extension
         ; Complains about a b c not being bound
)

I saw some older postings concerning this issue but the suggested solutions 
do not work. Can anyone provide simple examples of C code and Scheme code 
that lets me do this?

Thank you very much.

-- Agnes

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