# Traverse a tree using localize state
 $tree = [
     one =>
     two =>
     [   
         three_one =>
         three_two =>
         [   
             three_three_one =>
         ],
         three_four =>
     ],
     four =>
     [   
         [   
             five_one_one =>
         ],
     ],
 ];

 @path = ('q');
 rmap_to {
     if(ref $_) {
         local(@path) = (@path, 1); # ARRAY adds a new level to the path
         $_[0]->recurse(); # does stuff within local(@path)'s scope
     } else {
         print join('.', @path), " = $_ \n"; # show the scalar's path
     }
     $path[-1]++; # bump last element (even when it was an aref)
 } ARRAY|VALUE, $tree;

 # OUTPUT
 # q.1 = one 
 # q.2 = two 
 # q.3.1 = three_one 
 # q.3.2 = three_two 
 # q.3.3.1 = three_three_one 
 # q.3.4 = three_four 
 # q.4 = four 
 # q.5.1.1 = five_one_one