#!/usr/bin/perl -p
#12345678 1 2345678 2 2345678 3 2345678 4 2345678 5 2345
 s#\B\w+\B#join$,,(split$,,$&)[sub{($b,@*)=@_;$b=$*[$b]=
 pop while@_;@*}->(sort{(-1,1)[rand 2]}0..length$&)]#ge
#678 6 12345678 7 2345678 8 2345678 9 2345678 0 2345678