Binary mekso operator: group-theoretic conjugation (group action): maps inputs (X1, X to X2^(-X= \phi(X. Default: X3 = 1.
Assumes that the inverse of X2 is defined; inherits the group operator '*' (which is binary and left-groups/evaluates from the left) from context and assumes that it is defined for the given input pairs. X3 will typically be \pm 1. Negative 'exponents' denote inverses; an 'exponent' of 0 denotes the jdentity element for the group.