the File::Type module, although not bad, is clearly less accurate that file.

You've misunderstood something. The explicit purpose of File::Type is "to determine the MIME type of that file".

'image/jpeg' is a valid MIME type. 'JPEG image data, JFIF standard 1.01' is not. MIME types are important, eg, in internet transfers -- your browser decides how to treat something based on the MIME type in the http header.

The file command (which will give you a mime type too, if you use the --mime switch) can provide more detailed information in a "human readable" form but there is no protocol for this. It looks to me like someone has written a module porting "file" into perl tho: file.

However, since the author admits "this implementation is significantly slower than the C version" you might be better off just using backticks ;).