@SplitIce : basically, I'd prefer to avoid using another language/module : I have not complete freedom over server setup. LUA is not installed on current setup, and I think sysadmins might be reluctant to installing the LUA module just for me. :/

Would Rewrite+ Proxy + Substitution(s) make it, if I slightly modify my demand, so that I do not make "tests on header/content" before making changes. E.g., the aim would be to make requests on http://mysubdomain.mydomain.net get data on http://somewhere.else.net, changing the response body so that links to "http://somewhere.else.net/foo.bar.html" are changed into "http://mysubdomain.mydomain.net/tutu.html", plus other similar changes in the html source code ?

Thanks,
Yann