Data validation in UiPath App Studio

Yes it is absolutely possible by invoking a process

That is once user when gives the input it has to be passed to a process as input argument so that the process can validate the input and send back the result through out argument
With that you can validate whether the input is as expected or not

We cannot use a Regex directly in uipath apps
It has to be done through a process invoking

Hope this clarifies

Cheers @Teaf