Assuming you have data in given format. It would be easy to remember the parent. You don't need recursion in that case. You don't even need to mention the name of the parent. In the ouptut, you are given the order,level and parent information. Which you can format the way you like.
use strict;
use warnings;
my %Entry;
$Entry{-1} = '';
my @list;
my $id;
while(<DATA>){
chomp;
last if /OUTPUT/;
my $entry = $1 if /\b(\w+)$/;
my $level = () = $_ =~ m[\-]g;
my $item;
$Entry{$level} = $entry; #Remember the last entry
$item->{id} = ++$id;
$item->{name} = $entry;
$item->{parent} = $Entry{$level-1};
$item->{level} = $level;
push @list,$item;
}
foreach my $item (@list){
print join "|", map { $item->{$_} } qw(id level name parent);
print "\n";
}
__DATA__
foo
->bar
-->troz
->narf
__OUTPUT__
1|0|foo|
2|1|bar|foo
3|2|troz|bar
4|1|narf|foo
