[Closed] Validation Service Custom

Does someone know how to create a custom validation? https://docs.expressionengine.com/v5/development/services/validation.html#validation-service

That checks if a dot is at the end of the submitted value?

Example: expressionengine.com (invalid) expressionengine.com. (valid) expression. (valid) engine (invalid)

Is it also possible to combine build in validations? Example, allow alphaDash+alphaNumeric?

In a perfect world I would just use the regex for this but for some reason, the regex validation has never ever worked for me on any Expression Engine. Even when my same regex works fine in PHP. Not sure what is wrong but I was never able to use that validation field, the build in seems to work fine but are way to basic for my requirements.