Select Code to Download

  # As long as we have multiple keys, access the next subhash
   while (@keys > 1) {
      my $key = shift @keylist;
      $hashref = $hashref->{$key};
   }

while (@keylist > 1) {
    my $key = shift @keylist;
    $hashref = $hashref->{$key};
}

use strict;
use warnings;
...
[a1-a2-a3]
[jjj-kkk-lll-mmm]
{}

Output:
[a1-a2-a3]
[jjj-kkk-lll-mmm]
...
  a1  => { a2 => { a3 => 1 } },
  jjj => { kkk => { lll => { mmm => 2 } } },
}