tr -d axM-we might try `tr -d -axM', but that would fail because `tr' would try to interpret `-a' as a command-line option. Alternatively, we could try putting the hyphen inside the string, `tr -d a-xM', but that wouldn't work either because it would make `tr' interpret `a-x' as the range of characters `a'...`x' rather than the three. One way to solve the problem is to put the hyphen at the end of the list of characters