function vigenere($t,$k,optional $d)
dim $j,$r,$,$p,$o,$m,$y
 for $j = 65 to 90
  $ = chr($j)+$+chr($j+32)
 next
 $p = "0123456789"+$
 $m = 62 - (ucase($t+$k)=$t+$k)*26
 for $j = 1 to len($t)
  do 
   $ = left($k,1)
   $k = substr($k,2)+$
   $ = instr($p,$)
  until $
  $y = substr($t,$j,1)
  $o = $o+($y=" ") -$o*(0<instr('!.?',$y))
  $r = instr($p,$y)
  $vigenere = $vigenere+iif($r,substr($p, (iif($d,$m-$,$)+$r+o-1) mod $m+1,1),$y)
 next
endfunction