The other recursive example goes into an infinite loop.

I presume you mean mine. If so, no it doesn't: 

use strict;
use warnings;

sub print_tree {
   my ($tree, $depth) = @_;
   $depth ||= 0;
   my $indent = '...' x $depth;
   for (sort keys %$tree) {
      print($indent, /^\s*\z/ ? "<blank>" : $_, "\n");
      print_tree($tree->{$_}, $depth+1);
   }      
}

my %categories = (
    level1 => {
        'level1-1' => {},
        'level1-2' => {'level1-2-1' => {}},
        'level1-3' => {},
        },
    level2 => {'level2-1' => {}},
    );


print_tree(\%categories);

[download]
level1
...level1-1
...level1-2
......level1-2-1
...level1-3
level2
...level2-1

[download]

Unless, of course, you don't actually a have tree. Like I said before, %categories doesn't contain what you think it does.

In reply to Re^3: Printing a tree-view of a hash of hashes by ikegami
in thread Printing a tree-view of a hash of hashes by pdxperl

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