Depends on your system.

use File::Spec;
print File::Spec->canonpath("foo/../bar/../baz/")."\n";
[download]

\baz
[download]

On system without symlinks, canonpath collapses x/../y (although not always correctly, as shown above).

Update: Technically, NTFS does have symlinks, but most software act as if they don't exist, including File::Spec.