use Data::Dumper;
my @keys = (1,2,3);
my $href = 'somedata';
$href = {pop(@keys) => $href} while @keys;
#$href = {$_ => $href} foreach reverse @keys; # alternate solution, if @keys is constant or needed later
print Dumper( $href );
__END__
$VAR1 = {
          '1' => {
                   '2' => {
                            '3' => 'somedata'
                          }
                 }
        };