Right now simple string matches can be done with the RPC, if the string is at least two characters long. For more complex searches with regular expressions, I know of two methods:

* Search by the pattern's first two non-regex characters, and filter the results (unreliable, e.g. for inverse matches)
* Use packages.gz, grep it and do an info query with the results. This is limited by GET requests (see  FS#49089 ), and results are a few hours out of date.

It would be nice if the RPC and/or aurweb would support regex searches natively, instead of using hacks such as the above.