Function vigenere($t,$k,optional $d)

DIM $j,$r,$,$p,$o,$y

 For $j=65 To 90

  $=CHR($j)+$+CHR($j+32)

 Next

 $p = "0123456789"+$

 For $j = 1 To Len($t)

  Do 

   $ = Left($k,1)

   $k = SubSTR($k,2)+$

;   $y = InSTR($p,$)

;  Until $y

  Until InSTR($p,$)

  $ = SubSTR($t,$j,1)

  $o = $o+($=" ") -$o*(0<InSTR('!.?',$))  $r = InSTR($p,$)

  If $r

   $ = 62 - (UCase($t+$k)=$t+$k)*26

   $ = SubSTR($p,1+($+$r+(2*($d=0)-1)*($y-$o-2)-1) mod $,1)

  EndIf

  $vigenere = $vigenere + $

  Next

EndFunction