1. An apparatus for detecting presence of a selected complex string in a data stream, the apparatus comprising: at least one primary processor, and a respective memory device storing primary processor-readable instructions which cause said at least one primary processor to detect coherent strings of said selected complex string in said data stream; and at least one secondary processor pipelined to said at least one primary processor, and a respective memory device storing secondary processor-readable instructions which cause said at least one secondary processor to detect ambiguous strings interleaving said coherent strings in said data stream; thereby expediting detection of said selected complex string.