  The extension of pattern avoidance from ordinary permutations to those on
multisets gave birth to several interesting enumerative results. We study
permutations on regular multisets, i.e., multisets in which each element occurs
the same number of times. For this case, we close a gap in the work of Heubach
and Mansour (2006) and complete the study of permutations avoiding a pair of
patterns of length three. In all studied cases, closed enumeration formulae are
given and well-known sequences appear. We conclude this paper by some remarks
on a generalization of the Stanley-Wilf conjecture to permutations on multisets
and words.
