A method, system, and article are provided for evaluating regular expressions over large data collections. A general purpose index is built to handle complex regular expressions at the character level. Characters, character classes, and associated metadata are identified and stored in an index of a collection of documents. Given a regular expression, a query is generated based on the contents of the index. This query is executed over the index to identify a set of documents in the collection of documents over which the regular expression can be evaluated. Based upon the query execution, the identified set of documents is returned for evaluation by the regular expression responsive to execution of the query over the index.