perl caller(); where are the file names?

The  "latest" apache 1.X,  Apache::ASP, linux, perl 5.8.X

We are trying to get a stack dump with names, but caller  returns what looks like references.  Can we use these to obtain a file name?  (We suspect this is a security thing???  __FILE__ doesn't expand in our debugging statements either)

Thanks.   If this not the list for these questions, would you please suggest an alternative.