i1 : R = QQ[a..d, MonomialOrder=> GroupLex=>2];
i2 : a^-1 -1 o2 = a o2 : R
i3 : try c^(-1) else "failed" o3 = failed
The object GroupLex is a symbol.
The source of this document is in /build/reproducible-path/macaulay2-1.25.05+ds/M2/Macaulay2/packages/Macaulay2Doc/ov_monomial_orderings.m2:639:0.