@combined = sort {$a->[0] <=> $b->[0]} (@listone,@listtwo);

for ($i=0; $i<scalar(@combined); $i++) {
     if (substr($combined[$i][0],0,2) != substr($combined[$i][1],0,2)) {
          splice(@combined,$i+1,0,[substr($combined[$i][1],0,2)."0000",$combined[$i][1],$combined[$i][2]]);
          $combined[$i][1] = substr($combined[$i][0],0,2)."2359";
     }
}