Is this the actual code that you're trying to use? Because there seem to be a few problems with it.

• You use "opendir", but never read from the directory with "readdir"
• You use an array called @current_dir which is never populated (I think you probably need to populate it using a call to "readdir")
• You're using an operator (-eq) which doesn't exist in Perl. I think you want 'eq' instead
• Your new file name doesn't include D
• You don't actually rename the file at any point. You probably need to call the "rename" function at some point

Other than that, you're not defining any of your variables (with "my") which implies that you don't have "use strict" in your program. Programming something like this without "use strict" or "use warnings" is just silly. Why write code without all the help you can get from the compiler?