Validate anything with Regular Expressions

If you know what a Regular Expression is, did you know that the Parameters box of a Single Line Text item lets you enter any regular expression to validate that item's input?

Simply add the regular expression to the Parameters box and the form can only be submitted if the user enters text that matches the regular expression pattern.

If you require the field to be mandatory, you must still use the Mandatory item, as the regular expression is only validated if the user enters something into the form item.