Ruby: How to post a file via HTTP as multipart/form-data?

I want to do an HTTP POST that looks like an HMTL form posted from a browser. Specifically, post some text fields and a file field. Posting text fields is straightforward, there's an example right there in the net/http rdocs, but I can't figure out how to post a file along with it. Net::HTTP doesn't look like the best idea. curb is looking good.

[gabuchan]

rest-clientすげえええ！RubyでHTTP Postでファイルアップロード

[pokutuna]

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