Prevent search engines from indexing script URLs

Question

How to prevent search engines from indexing script URLs like:

domain.tld/?[whatever is here]

robots.txt

User-agent: *
Disallow: /?

does seem to work.

But still to allow indexing of the main page.

Answer 1

Use the URL-encoded "?" (%3D)

User-agent: *
Disallow: /%3D

source: http://www.robotstxt.org/norobots-rfc.txt