Internal Program Version: File::Which  1.270.0.5.42.0

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.

http://search.cpan.org/dist/File-Which