Common input devices: hidden form fields

This demo invokes the tutor5.py server-side script again, but hardcodes input data in the form itself as hidden input fields, instead of as parameters at the end of URL hyperlinks. As before, the text of this form, including the hidden fields, can be generated as part of the page output by another CGI script, to pass data on to the next script on submit; hidden form fields provide another way to save state between pages.