A regular expression is a pattern used to match text. Regular expressions are used for text processing in many programming languages (for example, Perl) and in UNIX utilities such as grep. They share common semantics and you are best looking online for additional information on regular expressions.

In SAT, the Regular Expression Replace string modifier lets you match a string against an regular expression and then replace it accordingly. Here is an example:

Source data:

Surname Forename                                                                                                              Smith      Bob                                                                                                                         Jones   Rob

If you pass Forename through this regular expression: Regular Expression: (Bob|Rob)

Replacement: Robert

Bob and Rob become Robert.

You must exercise caution with regular expressions and consider their impact across your source  data. Regular expressions do exactly what you ask. This can have undesired consequences. For example, if the example regular expression was used against the input string Robert, you would get Robertert. This is because it has matched Rob and replaced it with Robert. To avoid this, the regular expression would need to be (Bob|Rob)$. The $ symbol means match at the end of a string only.

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