If an entry in SearchEngines.php has multiple keyword parameters, this can be done by putting them into an array. But the path to the search engines result page only allows one uri what could lead to search engine results without any hits.
Proposal:
Allow an array as third parameter.
Example:
'www.allesklar.de' => array('Allesklar', array('words', 'cat_path'), array('s.php?words={k}', 'l.php?cat_path={k}'), 'utf-8'),
One other suggestion for SearchEngine.php
It might bring a slight performange increase when replacing all double quotes with single quotes (http://www.php.net/manual/en/function.print.php#66392).
The third parameter would only be useful if Piwik knew which path the keyword originated from. Piwik doesn't currently try to match the path in the urlref or store it. To do so would slow down the tracker.
The performance increase replacing double quotes with single quotes is negligible. Referring to the quoted benchmarks... take the difference between any two timings and divide by 160000 iterations. For example, (3937 ms - 1179 ms)/160000 is 0.0000172375 s or roughly 17 microseconds.