Using HTTP_REQUEST_METHOD_PUT to send plain TEXT ?

I'd like to send plain text to an existing file that I have a link to, replacing all text in that file.

makeWebRequest() specifying HTTP_REQUEST_METHOD_PUT seems like the way to do that, but I cannot find an example of how to send plain text.
The example that I found on the forum shows data to be sent going in the dictionary that is sent as the second parameter to makeWebRequest().
I want to send plain text.
Can someone describe how that can be done, or point me to an example ?
Thanks
Jeff