You can also do this kind of thing with a stack:

  sub parse {
     my @stack = @_;
     while (@stack) {
        my $node = pop @stack;
        print $node->{data};
        push @stack, @{$node->{children}};
     }
  }
[download]

Since Perl subroutine calls are so expensive this approach is often faster than recursion. Use Benchmark or Devel::DProf to be sure.

-sam