Problem using Numbers Regex.Extract function

I need help with the following Apple Numbers REGEX.EXTRACT formula that doesn’t return the word before a dot. Below are the text form of the arguments passed to the formula and the formula itself as well as a screenshot.

Pattern: \b\w+\b(?=\.)
String: 123. xpto.
Formula: REGEX.EXTRACT(“123. xpto.”, \b\w+\b(?=\.),1)