WML(5) on Linux
The text 2dd4fb108a9e, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
The widget meta-language file format for creating uil compilers "widget meta-language" "WML"