Ah - if you want to determine the "file type" (which is always guesswork), there is MMagic and File::MimeInfo.

Update: Looking at File::MMagic, it doesn't seem to have a magic number for recognizing core dump files. A likely faster way would be to determine the magic number(s) for core dump files on your system (maybe from the file magic file, maybe under /etc somewhere) and then write Perl code that reads just enough data to just (reliably) detect those core dump files.