!! +exec+ +jump+
$lst_tit whileval$lst_titend$type_exec
  同
  $(ref1)cmdlist_while_$(ref2)cmdlist_while_">while</a>,
  只是 $emph =$emphend ($emph==$emphend), 
  $emph!= $emphend 的比较是在 $emph string1$emphend 与 $emph string2$emphend
  的数值间进行, 而不是比较两个串.
