This isn't possible in normal Perl (with XS, Deparse, source filters, B::*, almost anything is possible). See, a variable name is just another reference to a value. It's like this:

            +----------+  
            |          |  
            | Variable |  
            |          |  
            +----------+  
                  |
                  |
                  V
              +-------+          +-----------+
              |       |          |           |
              | Value |<---------| Reference |
              |       |          |           |
              +-------+          +-----------+
[download]

There's no way "back" from the value to the variable (name). In fact, a value could have several names (think what Exporter does, or the aliasing that happens in a for loop), or no name at all.

Abigail