!! +exec+ +jump+
$lst_tit if$lst_titend$type_exec
  $(lst_syntax)if $emph string1 relation string2 $emphend<br/></tt>
  ... (多行内容)
 $ <tt>!endif</tt>
  $lst_mean 条件分叉: 当 relation$emphend 满足时,
  就执行 $emph!if$emphend 与 $emph!endif$emphend 中间的多行内容.
  $emph string1$emphend 与 $emph string2$emphend 前后的空格在比较前就被自动清除.

  !read help/if.phtml
