Mac::FileSpec::Unixish provides two functions, `nativize' and `unixify'
(both of which are exported by default), that will allow you to denote
and manipulate pathspecs in Unixish style, and let you convert these
pathspecs to and from the native OS's format for conveying such things.
It currently assumes that if you are not running under MacOS (as
reported in `$^O'), you must be on a Unix box.  If you want better, use
File::Spec -- in essence, Mac::FileSpec::Unixish is a cheap hack to get
around using File::Spec.