From File::Temp:

Note that there is no method to obtain the filehandle from the "File::Temp" object. The object itself acts as a filehandle. Also, the object is configured such that it stringifies to the name of the temporary file, and can be compared to a filename directly. The object isa "IO::Handle" and isa "IO::Seekable" so all those methods are available.

(with my emphasis).

Update: I used Acme::ESP when I wrote the above. I assumed you wanted to write to the tempfile and read it in again later.