use strict;
use warnings;
 
 sub init_doors
 {
   my @doors;
   for my $i (1 .. 100)
   {
     $doors[$i] = 'Closed';
   }
   return(@doors); 
 }
 
 sub toggle_door
 {
   my $door_ref = shift;
   if( $$door_ref eq 'Closed' )
   {
     $$door_ref = 'Open';
   } else {
     $$door_ref = 'Closed';
   }
   return $$door_ref; 
 }
 
 sub loop_through_doors
 {
  my @doors = init_doors();
   for my $pass (1 .. 100)
   {
     for my $visit (1 .. 100)
     {
       if (($visit % $pass) == 0)
       {
          toggle_door(\$doors[$visit]);
       }
     }
   }
 
   return(@doors); 
 }
 
 1;