#*
GRAMMAR PARSE TOKENS
  no tokens required, except to store odd/even state

HISTORY
  13 sept 2021: written

*#

 begin { add "odd*"; push; }
 read;
 [:alpha:] {
   pop;
   B"odd*" { push; get; put; clear; }
   B"even*" { push; swap; get; put; clear; }
 }
 ![:alpha:].!"" {
   pop;
   B"odd*" { replace "odd*" "even*"; push; }
   B"even*" { replace "even*" "odd*"; push; }
   swap; print; clear; swap; print; clear;
 }
 (eof) { get; print; }