All the reviews are very negative, but the module is self-contained and works well as far as it goes, which is in identifying file formats which were common ten years ago. It has more successes at identifying files than File::Type in my tests.
The formats it recognises are dated though, it doesn't recognise modern executable formats, XML, SVG, can't really distinguish when there are non-ASCII bytes in the file, but it does a better job than File::Type in several cases.
But it seems nearly abandoned judging from the bug reports. Perhaps this module is ripe for adoption.
Works for basic usage, but has quite a few problems. Plus it is not very performant. Doesn't seem to be maintained anymore.
The currently recommended module in this area seems to be File::LibMagic. Other alternatives include File::Type (gives less useful results), File::MMagic::XS (also not actively maintained? long standing bugs like failure to parse system magic file still persists), Media::Type::Simple (only maps MIME type from/to file extension).
This is a handy module for determining the the file type of a file by examining its contents. However, it some serious bugs (currently 19 are open), and hasn't been updated in two years. I personally ran into problems with bad results under mod_perl.
I would strongly suggest looking for alternatives before using this module. If you just need to check common web image formats, File::Type::WebImages is a simple module for that purpose. It was written precisely because File::MMagic had problems in mod_perl.