sub reduce_path ($) {
        # given a path which may contain multiple instances of ..
        # generate an absolute path
        my @path = split /\//, shift;

        my @new_path;
        while (scalar @path) {
                $_ = shift @path;
                if (/^\.\.$/o) { pop @new_path or
                        croak "I can't recurse past my root\n";
                } elsif (/^.$/o) {              # do nothing.
                } else { push @new_path, $_;
                }
        }
        return join ('/', @new_path);
}

# usage:
print reduce_path '/foo/bar/../baz', "\n";
print reduce_path '/foo/bar/../../baz', "\n";
print reduce_path 'foo/bar/baz/../', "\n";
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