use strict;
use warnings;
use Data::Dumper;

sub set_hash
{
   my $href = shift;
   my $val  = shift;
   my @key  = @_;
   $href->{$key[0]}{$key[1]}{$key[2]} = $val;
}

my %h;
set_hash(\%h, 42, 'a', 'b', 'c');
set_hash(\%h, 69, 'x', 'y', 'z');
print Dumper(\%h);

##</code><code>##

use strict;
use warnings;
use Data::Dumper;

sub set_hash
{
   my $href = shift;
   my $val  = shift;
   my @key  = @_;
   my $s = '$href->';
   for my $k (@key) { $s .= "{'" . $k . "'}" }
   $s .= "='" . $val . "'";
   my $rc = eval $s;
   defined($rc) or die "eval error: $@";
}

my %h;
set_hash(\%h, 42, 'a', 'b', 'c');
set_hash(\%h, 69, 'x', 'y', 'z');
set_hash(\%h, 'jock', 'shock');
set_hash(\%h, 'value', 'abc', 'def', 'ghi', 'jkl', 'xyz');
print Dumper(\%h);

##</code><code>##

$VAR1 = {
          'abc' => {
                     'def' => {
                                'ghi' => {
                                           'jkl' => {
                                                      'xyz' => 'value'
                                                    }
                                         }
                              }
                   },
          'x' => {
                   'y' => {
                            'z' => '69'
                          }
                 },
          'shock' => 'jock',
          'a' => {
                   'b' => {
                            'c' => '42'
                          }
                 }
        };