>  | Some files currently use a _ separator while others use ., as shown =20
>  | above.
>  | Is it there any rationale behind this difference?

>I added support for COPTS.<name> to <bsd.sys.mk> in rev 1.93 (2003/07/22)
>I don't recall why we switched from `_' to `.' as the separator.

Using '.' can be useful, since it allows :E and :R modifiers to
pick the variable apart.

--sjg