Advanced Webform users may want to consider ways to force certain types of validation that aren't available by default in the feature, but can be accomplished using what are called 'regular expressions' or a 'regex'.
Definition: A regular expression or regex can be described as a special text string for defining a search pattern.
How to use a regex in Webform
Scenario: a user would like to force a guest to only provide an email address with the 'ucdavis.edu' domain. This isn't possible in any of the default options but can be done using a regex pattern.