The content-based publish/subscribe (pub/sub) paradigm for system design is becoming increasingly popular, offering unique benefits for a large number of data-intensive applications. Coupled with the peer-to-peer technology, it can serve as a central building block for developing data-dissemination applications deployed over a large-scale network infrastructure. A key open problem towards the creation of large-scale content-based pub/sub infrastructures relates to efficiently and accu- rately matching subscriptions with substring predicates to incoming events. This work addresses this issue.