File::Which finds the full or relative paths to executable programs
on the system.
This is normally the function of which utility. which is typically
implemented as either a program or a built in shell command.
On some platforms, such as Microsoft Windows it is not provided as
part of the core operating system.
This module provides a consistent API to this functionality
regardless of the underlying platform.

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.