What thou needest, fellow monk who shall rename unnamed and anonymous, shall be not a regular expression.
No, instead you'll need some kind of a loop construct.
I don't know how good your math is, but with a word of 9 letters, there are 9! = 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 combination. This is because at the first position there are nine possible letters. The second position has only 8 possible letters and so on.
Your task will be to write a loop than can create all these combinations. And regex won't do that for you, AFAIK.