add_id 

Add an id to the element.

The id is an attribute (id by default, see the id option for XML::Twig new to change it. Use an id starting with # to get an id that's not output by print, flush or sprint) that allows you to use the elt_id method to get the element easily.

set_id_seed ($prefix) 

by default the id generated by add_id is twig_id_<nnnn>, set_id_seed changes the prefix to $prefix and resets the number to 1