1. A method comprising: receiving a sequence of values of text elements; determining, with one or more computing devices, a score for a text element value of the sequence, where the score is related to the probability of a particular text element value equaling one or more given values, and where said probability is based on sequences of text element values that are consistent with a defined format; comparing, with the one or more computing devices, the score to a threshold; when the score is below a threshold, modifying, with the one or more computing devices, the value of the text element to form a modified sequence of text element values; processing, with the one or more computing devices, the modified sequence of text element values with a set of instructions; and testing, with the one or more computing devices, a performance characteristic of the set of instructions when the set of instructions process the modified sequence of text element values.