You're asking about the values, not the keys ;-)

Actually, I think the original poster was asking about the keys and not the values.

If your code does this ...

use LWP::Simple;

... then once the Simple.pm file has been located via @INC the pathname will be stored in %INC as the value associated with the key 'LWP/Simple.pm'.

It is my understanding that a package name is always converted to a key by replacing '::' with '/' and appending '.pm' regardless of the naming conventions of the platform where the code is running. The full pathname to the file (ie: the value in %INC) is in a platform dependent format.

So the answer to the original question: No the keys in %INC are not OS dependent.