This format is obsolete, but is still accepted. It combined the
functions of INST and TLIST, taking a series of
transformations and a single Geom (unit) object, and replicating
the object under each transformation.
GROUP ... < matrices > ... unit { oogl-object }
is still accepted and effectively translated into
INST
transforms { TLIST ... <matrices> ... }
unit { oogl-object }