18. The search engine of claim 16 , wherein: a first of the commands comprises a bitcheck command embodying the specified set of characters; and a first of the co-processors is dedicated to execute the bitcheck command to generate a compliance signal indicating whether a selected input character is a member of the specified set of characters.
19. The search engine of claim 18 , wherein: the bitcheck command contains a bitmap including a plurality of compliance bits, each indicating whether a corresponding reference character of a general set of characters is a member of the specified set of characters; and the first co-processor references each of the input characters to a corresponding compliance bit in the bitmap to generate the compliance signal.