more sensible way to change directories

 Perl's chdir() has the unfortunate problem of being very, very, very
 global. If any part of your program calls chdir() or if any library you
 use calls chdir(), it changes the current working directory for the
 whole program.
 .
 This sucks.
 .
 File::chdir gives you an alternative, $CWD and @CWD. These two variables
 combine all the power of chdir(), File::Spec and Cwd.