$lvalue ?<:=  $rvalue; 
$lvalue ?>:=  $rvalue; 
$lvalue ?<=:= $rvalue; 
$lvalue ?>=:= $rvalue;
$lvalue ?lt:= $rvalue; 
$lvalue ?gt:= $rvalue; 
$lvalue ?ge:= $rvalue; 
$lvalue ?le:= $rvalue;