Custom validation for multiple variables

We have defined three individual variables for the terraform module and all variables are optional but at least one of the three variables should be added by the user. So there is the requirement to add validation which checks that whether the users have given at least one of the three variables or not. We have checked the terraform documentation and found that we can add the validation for individual variables in the validation block but we can not add common validation for these three variables. So is there any way to handle these types of situations in the terraform?