Operations on Custom properties before replacement

I want to do response assertions using regular expressions. These regular expressions need to contain certain parts that are defined using custom properties and request arguments, i.e. they contain placeholders like

${#Project#propertyA

or

${propertyB}

The service that I need to test contains these properties as part of the response but - unfortunately - converted to all uppercase. To be able to create a properly matching pattern I need a way to apply some function to the property, i.e. something like

${propertyX.toUpperCase()}

Similarly, to describe a proper JSON response also need to change all "/" characters in a property to "\/" (back-slash forward-slash), i.e. somthing like

${propertyY.replace("/", "\/")}

Is there such a possibility to "massage" a property before applying it an assertion?