I am guessing some script or tool used upstream is doing an unsafe
search-and-replace for '@' with TAB, and accidentally changing these.
They seem to have been creeping into the repo for years.
I produced this fix commit automatically with:
sed -i 's|\t\([bcdgmnoruwyBCDGMRWY]\)|@\1|g' tba/*/*.*
...and then a few files' changes had to be undone.
I looked through all of the rest, and they look like correct fixes.
I also ran all the other letters, and they only make incorrect "fixes".
