You want to check the file's magic numbers. I thought there was a module that checked it, but I can't find it ATM (Video::Info::Magic uses magic numbers, but it's for video file types).

If a module can't be found, you can always execute the magic program itself and grab its output. I usually prefer to avoid relying on an external program, but in this case you may have no choice.

----
I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident.
-- Schemer

Note: All code is untested, unless otherwise stated