Is it possible to process HTML forms without an own webserver stack?

I would like to know, that how is it possible to process a submitted HTML form without my own webserver and the appropriate web stack, and also provide a return value in the browser, after the submitting happens. If one use an own webserver and using let's say Ruby or Pyhton language, then it is relatively easy to make a program, script, which processes the form's data, and provides an output which is displayed in the browser. But what can I do if I have no webserver with the full web stack? Is there some general web service (Google or other), where I can "host" such form processing scripts, written in any language or made by some wizard-like mechanism?

My goal would be: blog visitor enters 5 codes (similar to hash-codes), for example into a textarea, and then submits it, and if all the five codes are accepted by the processing script as valid codes, then another code, a voucher-code would be shown on the blog, which the visitor can use for something (for discount). The valid codes which should be accepted by the form processing program would be stored even in the script itself, or in a text file, database, spreadsheet, etc.