`Orcish Maneuver'

Memoizing is very useful for sort comparison functions
Example: Sort strings like May 14, 1997 into chronological order.
Obvious method:

         %m2n = 
           ( jan => 0, feb => 1,  mar => 2,
             apr => 3, may => 4,  jun => 5, 
             jul => 6, aug => 7,  sep => 8, 
             oct => 9, nov => 10, dec => 11, );

         sub compare_dates {
           my ($am, $ad, $ay) = 
             ($a =~ /(\w{3}) (\d+), (\d+)/);

           my ($bm, $bd, $by) = 
             ($b =~ /(\w{3}) (\d+), (\d+)/);

                      $ay  <=>         $by  
           || $m2n{lc $am} <=> $m2n{lc $bm} 
           ||         $ad  <=>         $bd;
         }