To answer the question, I followed these steps:

<ul>
  <li><b>Identified the countries</b> that make up Southern Africa to ensure the correct group was being analyzed.</li>
  <li><b>Found the relevant economic indicator</b> by searching for the official exchange rate against the US dollar, as this was the specific data needed for the year 2009.</li>
  <li><b>Retrieved the official exchange rate values</b> for each Southern African country for 2009, gathering the necessary data points for the calculation.</li>
  <li><b>Calculated the total sum</b> of the exchange rates from all the countries to prepare for averaging.</li>
  <li><b>Divided the total by the number of countries</b> to find the average official exchange rate for the region in 2009.</li>
</ul>

In summary, I systematically gathered the exchange rate data for each country in Southern Africa for 2009, summed them up, and calculated the average.

<b>The average official exchange rate against the US dollar for Southern African countries in 2009 was approximately 8.22 (local currency units per US dollar).</b>