\ rot13 in forth
\ by Teknovore/1997
: caprot ( rotate capital letters )
    78 <
    if
	13 + emit
    else
	13 - emit
    then
;

: lowrot ( rotate lowercase letters )
    110 <
    if
	13 + emit
    else
	13 - emit
    then
;

: rot13
    dup dup dup
    64 > swap 91 < and
    if
	caprot
    else
	dup dup
	96 > swap 123 < and
	if
	    lowrot
	else
	    drop
	    emit
	then
    then
;

variable foo

: dorot
    begin
	key
	dup
	foo !
	dup
	4 = 0=
	if
	    rot13
	then
	foo @ 4 =
    until
;

dorot
cr
bye