$use StdIO;

$tfunc Perm (e) (e) = ;

Perm (e1) (e2) =
{
  e2 : \{
    ea tx eb,
      <Perm (e1 tx) (ea eb)>,
      $fail;
    =
      <PrintLn e1>
    ;
  };;
};

Main = <Perm () ('12345')>;