  Let $a$ be a non-invertible transformation of a finite set and let $G$ be a
group of permutations on that same set. Then $\genset{G, a}\setminus G$ is a
subsemigroup, consisting of all non-invertible transformations, in the
semigroup generated by $G$ and $a$. Likewise, the conjugates $a^g=g^{-1}ag$ of
$a$ by elements $g\in G$ generate a semigroup denoted $\genset{a^g | g\in G}$.
We classify the finite permutation groups $G$ on a finite set $X$ such that the
semigroups $\genset{G,a}$, $\genset{G, a}\setminus G$, and $\genset{a^g | g\in
G}$ are regular for all transformations of $X$. We also classify the
permutation groups $G$ on a finite set $X$ such that the semigroups $\genset{G,
a}\setminus G$ and $\genset{a^g | g\in G}$ are generated by their idempotents
for all non-invertible transformations of $X$.
