Mystery MML command

We found a few MML error messages that reference %: "Missing %" and "Duplicate %" I haven't been able to trigger these errors, or use % without causing another error (usually it's just "Unknown command") I'm guessing that % is part of another command, for example, something like X123,456% because the messages imply that it is required ("Missing %") and you can only use one ("Duplicate %") so it can't just be some option like & or _ (and it's definitely not a valid command on its own). It's not referenced anywhere in the manual (but there are other undocumented MML features), and there is no known MML that uses %.

Where did you find this string? Do you know it's actually MML, or something else? The occurrence of % reminds me of this but it's unlikely to be related.

Snail: no, this doesn't do any actual checking. It's just a sort of string table. Walking up the call trace leads to another error handling print for display the line and position in the MML, which is then orphaned (presumably by bad decompile into a dynamic call somewhere)

It's a table but broken down into a bunch of ifs? Uhh okay. Whatever they fancy.