[exim] wildcard recipients to script

I run a photo-sharing site and I want to enable uploads by email.

Users will get an address like m-1234abcd5678efgh@???

I want exim4 (on Debian stable) to route m-*@??? to a script.

If the script has output, bounce the message.

It seems like this shouldn't be hard to do, but I couldn't readily see from
the docs how to set up wildcard or regexp recipients. What's the best way
to do this?


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