I don't know if they could do a try/fallback or if one is available as a setting (I haven't looked), but apparently they don't by default; Scryer Prolog: ?

I don't know if they could do a try/fallback or if one is available as a setting (I haven't looked), but apparently they don't by default; Scryer Prolog: ?- X = '.'(1,'.'(2,'.'(3,[]))). X = [1,2,3]. SWI Prolog 9: ?- X = '.'(1,'.'(2,'.'(3,[]))). ERROR: Type error: `dict' expected, found `3' (an integer)