Okay. I didn't want to do it, since that means 65535 lines of data to look through to verify that all of my tabs were in the right place. However, if I would have paid more attention to the error, I would have seen that it happens on line 1 of __DATA__. Sure enough, line 1 had spaces instead of a tab. Fixed the tab, lost the error.
/me will be wearing a big "Idiot" sticker on my forehead the rest of the day. *sigh*