On Unix, a tool called 'file' has a large and growing database of file type heuristics. File::Type is a Perl module equivalent. These read just enough of a file to make a solid guess as to the type, and report it.

I feel that the File::MMagic module provides a more mature alternative to the File::Type module to provide file-like functions. This module has the added advantage in that it can read in the same magic files as those employed for file to extend its recognition profile.