I could never figure out how to parse something between evaluating inside out (strict) and outside in (lazy, well ignoring the complexity around multiple evaluations). Every informal definition I thought of seemed too weak to be useful. This was due to the core problem that generally speaking the coder needs to know if a particular expression will be evaluated using local reasoning (e.g. if I get here will `A` or `B` be evaluated) and without by-demand or strict you can't make that guarantee.

Taking a quick look at pH it looks like they haven't figured out the semantics quite yet so that isn't a true answer to the question either.

Have there been any other non-strict languages with well known semantics? (Excluding things like Prolog)