In the context of parsing operations, a regular expression is an expression that you can use to identify one or more strings in input data. The Parser transformation writes identified strings to one or more output ports. You can use regular expressions in Parser transformations that use token parsing mode.
Parser transformations use regular expressions to match patterns in input data and parse all matching strings to one or more outputs. For example, you can use a regular expression to identify all email addresses in input data and parse each email address component to a different output.