$template->param(foo_input =>
      "<input type=checkbox name='foo'" . $foo_checked ? " checked>" : ">");
  ...
  <TMPL_VAR foo_input>

##</code><code>##

  $template->PARAM(foo_checked => $foo_checked);
  ...
  <input type=checkbox name="foo" <TMPL_IF foo_checked>checked</TMPL_IF>>

##</code><code>##

  $template->param(foo_checked => $foo_checked);
  ...
  <TMPL_IF foo_checked>
  <input type=checkbox name="foo" checked>
  </TMPL_ELSE>
  <input type=checkbox name="foo">
  </TMPL_IF>

##</code><code>##

  <input type=checkbox name="foo">

##</code><code>##

  <TMPL_IF false><input type=checkbox name="foo"></TMPL_IF><TMPL_VAR foo_input>

##</code><code>##

  $template->param(false => 0);