The Regular Expression node allows you to match variables to a regular expression pattern and define what action comes next (either route the user to a new step in the workflow or trigger a new workflow).
Below are some examples of commonly-used regular expressions:
Evaluates that an input is in the date format yyyy-mm-dd
Evaluates that an input is alphanumeric with a minimum of 4 and a maximum of 16 characters in length (e.g. a user name)
Evaluates that an input is a 4-digit numeric code
Evaluates that an input is either 1 or 2