v='*.z'

# Buggy:
# the problem is that expansion rules of LHS and RHS of ~=
# should not be the same: in RHS, "$v" and "*" should escape metas
# (currently "$v" does not),
# but in LHS, they should _not_ do that
# (currently "*" does). Thus these cases fail:
[[ a.z == "$v" ]]; echo 4:no:$?	# BUG: "$v" expands to *.z
[[ "*".z == ?.z ]]; echo 5:YES:$?	# BUG: "*" expands to \*