In this paper we propose a new query that can be more appropriate in these collections, which we call contextual pattern matching. The basic query of this type gives, in addition to P, a context length l, and asks to report the occurrences of all distinct strings XPY, with |X|=|Y|=l.
While this query is easily solved in optimal time and linear space, we focus on using space related to the repetitiveness of the text collection and present the first solution of this kind. Letting r' be the maximum of the number of runs in the BWT of the text T[1..n] and of its reverse, our structure uses O(r' log(n/r')) space and finds the c contextual occurrences XPY of (P,l) in time O(|P| log log n + c log n). We give other space/time tradeoffs as well, for compressed and uncompressed indexes.