The Permute(s, perm) command applies a given permutation perm to the string s.

The permutation perm must be a permutation of the integer $1..\mathrm{length}\left(s\right)$, given as a list.

All of the StringTools package commands treat strings as (null-terminated) sequences of $8$-bit (ASCII) characters.  Thus, there is no support for multibyte character encodings, such as unicode encodings.

$\mathrm{with}\left(\mathrm{StringTools}\right)\:$

$\mathrm{Permute}\left(''abc''\,\left[1\,2\,3\right]\right)$

$''abc''$

$\mathrm{Permute}\left(''abc''\,\left[1\,3\,2\right]\right)$

$''acb''$

$\mathrm{Permute}\left(''abc''\,\left[2\,1\,3\right]\right)$

$''bac''$

$\mathrm{Permute}\left(''abc''\,\left[2\,3\,1\right]\right)$

$''bca''$

$\mathrm{Permute}\left(''abc''\,\left[3\,1\,2\right]\right)$

$''cab''$

$\mathrm{Permute}\left(''abc''\,\left[3\,2\,1\right]\right)$

$''cba''$

$\mathrm{Permute}\left(''abc''\,\left[2\,1\,4\,3\right]\right)$

Error, (in StringTools:-Permute) [2, 1, 4, 3] is not a permutation of 1 .. 3

$\mathrm{Permute}\left(''abc''\,\left[2\,3\,3\right]\right)$

Error, (in StringTools:-Permute) [2, 3, 3] is not a permutation of 1 .. 3

AllPermutations := proc( s::string )
    local    p;
    seq( StringTools:-Permute( s, p ),
        p = combinat[ 'permute' ]( length( s ) ) )
end proc:

$\mathrm{AllPermutations}\left(''uvw''\right)$

$''uvw'',''uwv'',''vuw'',''vwu'',''wuv'',''wvu''$

$\mathrm{AllPermutations}\left(''abcd''\right)$

$''abcd'',''abdc'',''acbd'',''acdb'',''adbc'',''adcb'',''bacd'',''badc'',''bcad'',''bcda'',''bdac'',''bdca'',''cabd'',''cadb'',''cbad'',''cbda'',''cdab'',''cdba'',''dabc'',''dacb'',''dbac'',''dbca'',''dcab'',''dcba''$