my $mergedYesterday = join '/', ( split ' ', $yesterday )[ 2, 1, 4 ];
          ^                 ^                     ^        ^  ^  ^ 
          |                 |                     |        |  |  | 
          |                 |                     |        |  |  + - 2012
          |                 |                     |        |  + - Nov
          |                 |                     |        + - 11
          |                 |                     + - Sun Nov 11 19:31:46 2012
          |                 + - Use same delimiter as in log records
          + - 11/Nov/2012