The focus of this module is correctness and portability. As a consequence platforms where the current directory is implicitly part of the search path such as Microsoft Windows will find executables in the current directory, whereas on platforms such as UNIX where this is not the case executables in the current directory will only be found if the current directory is explicitly added to the path.
If you need a portable which on the command line in an environment that does not provide it, install App::pwhich which provides a command line interface to this API.