RegExp Substitution

Without resorting to the use of String.toUpperCase(), is there a good way to accomplish the following with an AS3 RegExp?

tr/[a-z]/[A-Z]/

I’ve tried (and failed so far) using a RegExp in conjunction with String.replace(). Has anyone been able to accomplish traditional regex substitution or translation? It seems like the second parameter to String.replace() would also have to be a RegExp.