Write a python script to spider the wiki for all pages that contain references to ab(c)-xy(z)-stems (e.g., {{#lst:Apertium-tuk-tur/stats|tuk-tur-stems}} as in the Turkic languages page) and change them to ab(c)-xy(z)_stems. You should check all pages linked to the pages listed in Category:Datastats (i.e., pages like this one) for such text. You can use our current wiki bot's code—it's probably pretty easy to call functions from it like editPage() or login() to edit the wiki. Contact your mentor for a username and password to run the bot with (and then don't tell it to anyone!).