public Pattern getCompiledRegionRegex() {
        Pattern result = compiledRegionRegex;
        if (result == null) {
            result = Pattern.compile(regionRegex);
            compiledRegionRegex = result;
        }
        return result;
    }
Get the compiled region regular expression of the partition.

@return the compiled region regex.
smithy-aws-endpoints/src/main/java/software/amazon/smithy/rulesengine/aws/language/functions/partition/Partition.java