left:auto;
This will default the left back to the browser default.
So if you have your Markup/CSS as:
<div class="myClass"></div>
.myClass
{
position:absolute;
left:0;
}
When setting RTL, you could change to:
<div class="myClass rtl"></div>
.myClass
{
position:absolute;
left:0;
}
.myClass.rtl
{
left:auto;
right:0;
}