That does not make any sense. lvalue and rvalue are contexts, how do you want to tag them with properties? A variable can be used as an rvalue in one statement, and as lvalue in the next.

You must have a background in Functional Programming, where values never change

Values don't change in Perl either. If you do think values change, please give a code example. Functional Programming doesn't have side effects, hence no variables changing value.

-- Abigail