Header modification

[Anonymosity]

Is there any way to modify any of the fields in Opera's request header conditionally? I am especially interested in conditional modification of the referer. I would like the referer to be removed either if Opera is requesting images (as Firefox can) or if it is following links to different sites from its current one. Both would be really nice, but either one would be acceptable.

UserAgent: Opera/9.80 (Macintosh; Intel Mac OS X; U; en) Presto/2.6.30 Version/10.63