Code:
alias _hint {
  var %i = 0,%a,%b = $regsub($2-,/\w/g,*,%a),%p
  bset -t &b 1 %a
  while (%i < $1) {
    %p = $pos($bvar(&b,1-).text,*,$r(1,%b))
    bset -t &b %p $mid($2-,%p,1)
    dec %b
    inc %i
    set %hint $+ %i $bvar(&b,1-).text
  }
}


/_hint <number of hints> <answer>

It sets variables named %hintN, so %hint1 is the first hint, %hint2 the second and so on