If some one wrote grep in Perl, and they are considered incapable of writing the same in Python. I have now doubts on the evaluation capabilities of the hiring committee.

Software world is huge. You will have learn, forget, relearn and learn new things all the time. You don't change programmers every time a new requirement on a new technology comes along. Which is why if some can write grep in Perl, they can also with a little yak shaving write grep in Python as well. Then in Golang, Java etc. And if some one wrote grep in Scheme, they can also write it in Clojure, or Common Lisp.

Programming languages of a particular style(C, Lisp based, ML family etc) don't change much in semantic features in their categories.

The point of a take home project is to see if a person can get things done.