Use a stack to enumerate all permutations of a string. Suppose you want to find all permutations of the string meat.
Pseudocode:
Push the string +meat on the stack.
While the stack is not empty
Pop off the top of the stack.
If that string ends in a + (such as tame+)
Remove the + and add the string to the list of permutations.
Else:
Remove each letter in turn from the right of the +.
Insert it just before the +.
Push the resulting string on the stack.
For example, after popping e+mta, you push em+ta, et+ma, and ea+mt.