Is possible to upload a file?
Is possible do copy the HTML of a page?
Is possible to send the text inserted in a text box for a email?
If you combine ajax with some PHP the answer is YES to your questions.
And as you were not asking about how to do it I guess you're happy with that answer..
Otherwise it would have been a good idea to put some more effort in writing your questions.
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do you have an example?
No, I'm sorry. Actually I haven't really checked out the AJAX feature in Construct 2. But as I'm a freelance web developer I've used AJAX an PHP together in many website project.
EDIT: I just noticed that the AJAX feature in Construct 2 seem to be focused only for retrieving content and not passing variables. So I might have been wrong in what I told you earlier.
But the best idea is to wait and see if someone else answers I think. I just began using Construct 2 so I haven't really got very big knowledge about the plugins available and such.