Cwd provides functions for determining the pathname of the current working
directory. It is recommended that getcwd (or another *cwd() function) be used in
all code to ensure portability. By default, it exports the functions cwd(),
getcwd(), fastcwd(), and fastgetcwd() (and, on Win32, getdcwd()) into the
caller's namespace.

File::Spec is designed to support operations commonly performed on file
specifications (usually called "file names", but not to be confused with the
contents of a file, or Perl's file handles), such as concatenating several
directory and file names into a single path, or determining whether a path is
rooted.