computeExpression LTRIM:  I have an expression that is ltrim('Primary_Sales_Rep.Region__c', "Sales - ").  So, I want to remove "Sales - " from the region field.  This seems to work for many of the values like Sales - Carolinas becomes "Carolinas", but if there is a value that start with S, like Sales - Southeast, then I get "outheast" and even one that starts with an "S" but doesn't have "Sales - " gets trimmed to "oftware & Carousel Service Contracts".  see attachment.  Is there a better function to use to trim the "Sales - " off?