Code:
alias countcs {
  /set -u0 %count 0
  /set -u0 %l 1
  while (%l <= $len($1)) {
    if ($2 isincs $mid($1, %l, 1)) { /inc -u0 %count }
    /inc -u0 %l
  }
  return %count
}


-KingTomato