9. The computer program product of claim 7 , wherein the tag is one of an ampersand, an asterisk, and a question mark.
7. A computer program product for optimizing generation of a regular expression utilized for entity extraction, the computer program product comprising: a computer readable tangible storage device and program instructions stored on the computer readable tangible storage device, the program instructions include: program instructions to receive at a server, an input from a user of the server, the input enabling at least a first performance optimization parameter; program instructions to receive, from a user of a client computer, a query comprising a plain text word; program instructions to receive, at the server, data extracted from an electronic repository that is communicatively connected to the server, the data describing probabilities of spelling errors based, at least in part, on a number of syllables in the plain text word; program instructions to initialize, at the server, the first performance optimization parameter based, at least in part, on the received data and the input enabling at least the first performance optimization parameter; program instructions to optimize performance of generating the regular expression, at the server, by, at least in part, executing program instructions to identify, using the first performance optimization parameter, a syllable within the plain text word that has a high probability of at least one of an incorrectly substituted and transposed character within a spelling of a word having a same number of syllables as the plain text word; program instructions to select, at the server, a character in the syllable identified; program instructions to identify, at the server, a group of characters from a confusion matrix that are commonly confused with the character selected; program instructions to generate, at the server, a set of characters for the character selected, wherein the set of characters begins with the character selected followed by and ending with the group of characters from the confusion matrix; program instructions to determine, at the server, that a probability of omitting the character selected exceeds a threshold, and in response, associating, at the server, a tag with the set of characters; program instructions to generate, at the server, a regular expression by concatenating the set of characters with one or more additional sets of characters; program instructions to, based, at least in part, on the tag and the regular expression, search, at the server, the electronic repository for text data describing a spelling of the plain text word in which at least one of (i) the character selected and (ii) one or more characters of the group of characters from the confusion matrix is omitted; and program instructions to provide, to the user of the client computer, search results based on the regular expression.