The below snippet with tell you the percentage of capital letters , lowercase letters or both. It will only take into account letters in the string being checked.

Update: Removed variables and placed $regex inside $calc itself. Also made the % optional for each version. ( June 9th '08 )

Update: Redid the code a bit to make it shorter and easier to use. ( August 27th '08 )

;http://www.hawkee.com/snippet/3325/ ( based off of )
;--- Usage ----------------
;--- $iscaps(string).u <-- %caps
;--- $iscaps(string).up <-- %caps /w % after number
;--- $iscaps(string).l <-- %lowercase
;--- $iscaps(string).lp <-- %lowercase /w % after number
;--- $iscaps(string) <-- %caps , %lowercase
;--- $iscaps(string).p <-- %caps , %lowercase /w % after numbers
;--------------------------

;http://www.hawkee.com/snippet/3325/ ( based off of )
;--- Usage ----------------
;--- $iscaps(string).u  <-- %caps
;--- $iscaps(string).up  <-- %caps /w % after number
;--- $iscaps(string).l <-- %lowercase
;--- $iscaps(string).lp <-- %lowercase /w % after number
;--- $iscaps(string)  <-- %caps , %lowercase
;--- $iscaps(string).p  <-- %caps , %lowercase /w % after numbers
;--------------------------
alias iscaps { 
  if ($isid) {
    if (u isin $prop) { 
      return $+($round($calc( $regex($1,/[A-Z]/g) / $regex($1,/[A-Z]/gi) * 100),2),$iif(p isin $prop,$chr(37)))
    }
    if (l isin $prop) { 
      return $+($round($calc( $regex($1,/[a-z]/g) / $regex($1,/[A-Z]/g) * 100),2),$iif(p isin $prop,$chr(37)))
    }
    if (!$prop || $prop == p) {
      return $+($round($calc( $regex($1,/[A-Z]/g) / $regex($1,/[A-Z]/gi) * 100),2),$iif(p isin $prop,$chr(37))) , $&
        $+($round($calc( $regex($1,/[a-z]/g) / $regex($1,/[A-Z]/gi) * 100),2),$iif(p isin $prop,$chr(37)))
    }
  }
}