For Perl, it is very easy to convert recursive program into its iterator version.

The only thing you need, in order to accomplish this conversion easily, is 'stack'. Perl by default suppots stack in its core, thanks to the ability to pop() and push() against a list.

To convert:

• As a start point, some element(s) need to be processed is push() onto the stack
• For each iteration:
  • pop() one element out of the stack, if nothing to pop(), the process is finished; otherwise process this element
  • If there are child element(s) need to be processed, push() them onto the stack