my %classrooms;
$classrooms{classroom}{students}[0]{ln}
   = 0; #d3

$classrooms{classroom}{students}[0]{id}
   = 0; #d3

$classrooms{classroom}{students}[0]{age}
   = 0; #d3

$classrooms{classroom}{students}[0]{fn}
   = 0; #d3

$classrooms{classroom}{students}[1]{ln}
   = 1; #d3

$classrooms{classroom}{students}[1]{id}
   = 1; #d3

$classrooms{classroom}{students}[1]{age}
   = 1; #d3

$classrooms{classroom}{students}[1]{fn}
   = 1; #d3