Convert last word to lower case. Note Meta-- is Meta-minus.
Convert last word to all upper case.
Convert last word to lower case with capital initial.
A very common error is to type words in the wrong case. Because of this, the word case-conversion commands M-l, M-u, and M-c have a special feature when used with a negative argument: they do not move the cursor. As soon as you see you have mistyped the last word, you can simply case-convert it and go on typing. See Case.