Template using if else

Can we use OR AND in the IF's
something like
<!-- IFDEF: SRCH_NOT_ROBOT AND LOGGED_ADMIN -->

Also can we use =
Like
<!-- IFDEF: SRCH_NOT_ROBOT = 'yes' -->

<!-- IFDEF: SRCH_NOT_ROBOT = 'yes' -->
There is no use for this.
If you want to have true value just use this
<!-- IFDEF: SRCH_NOT_ROBOT -->
....
$ft->assign("SRCH_NOT_ROBOT",1);

opposite
$ft->assign("SRCH_NOT_ROBOT",0);

The condition is evaluated in php not in the template.