Ha! I was just getting ready to post the same script Only mine has different syntax.
DeathClock mm/dd/yyyy m|f s|n bmi. s|n, bmi optional. Then I just had !pessimistic
!sadistic !optimistic to refer to the last call. Here is my bmi alias anyway ;/

;Syntax $1 = weight in lbs $2 = height in inches
alias bmi {
  return $round($calc(($1 * 703) / ($2 * $2)),0)
}

At least I looked first this time ;/