relativepath... does it work?

what does this object do?
i would think that i could an argument like:

[relativepath ../]
and it would output the path w/ a single dir up from in input path.

or

[relativepath ./myfolder]
[relativepath myfolder]
to get dig into a folder named 'myfolder' from a given input path.

does it not do this? how, or why not?
i am about to write a super ugly max-style thing that does it, but before i do, i wanted to ask this question.

i know about js and how to convert a path into an array... this is not what i am looking for.

thanks,
jml