Hi Soumya, Yep, for the future you probably want the user support list ( http://httpd.apache.org/lists.html#http-users).
However, to be helpful I think the answers to your questions would be 1) Apache 1.3 uses POSIX based regular expressions, and apache 2.x uses the PCRE library, so they're perl compatible. 2) RewriteCond %{QUERY_STRING} (^|&|;)Operation=(((rain|spain|plain),)*(rain|spain|plain))($|&|;) RewriteRule . - [E=OPERATION:%2] There are lots of ways to optimise the above, but I've kept it to something relatively simple for easy reading... If you wanted anything more complicated than that in a single rule, I'd suggest looking at writing your own internal map function. This list could help you with that. HTH, Ross Heritage. On 21/8/07 17:04, "Soumya Sanyal" <[EMAIL PROTECTED]> wrote: > Hello, > This might not be the most appropriate forum to field this question - but > I'm having serious issues with the formulation of a regex for Mod Rewrite. I > actually have a couple of questions to ask : > > 1> What is particular flavor of the regex engine being used by Mod Rewrite - > there are ever so slight variations in the different regex engines, e.g. > linux grep vs perl grep etc. > 2> I'm having trouble formulating a good compact regex to represent the > following problem : > > I want my RewriteCond to be conditioned on the %{QUERY_STRING} to contain > only the powerset of a group of words e.g. > > Hence if my set is say {rain,spain,plain} > > The RewriteCond should say yes to the following : > http://foo.bar.com/?Operation=rain,spain > http://foo.bar.com/?Operation=plain,rain,rain > http://foo.bar.com/?Operation=plain,rain,spain > > But not : > http://foo.bar.com/?Operation=rain,spain,mainly > > Help please ?