https://bugs.winehq.org/show_bug.cgi?id=38558
--- Comment #5 from katsunori.kumatani@gmail.com --- It would certainly be a great thing if the builtin cmd would work as well as the one supplied by Microsoft!
At this point, another possibility for this bug is more like some buffer overflow in cmd.exe (i.e. bug in Microsoft's cmd) that Windows just silently ignores by coincidence or something...
Btw, maybe a bit esoteric, but don't forget that in batch for loops, ? is a valid name for a variable too (i.e. %%? instead of %%a or %%b and so on). :)