#!/usr/bin/perl

use strict;
use Graph::Undirected;
use Graph::Traversal::DFS;
  
my $g = Graph::Undirected->new;
  
$g->add_edge('a', 'b');
$g->add_edge('b', 'c');
$g->add_edge('c', 'd');
$g->add_edge('c', 'z');
$g->add_edge('d', 'e');
$g->add_edge('c', 'q');
$g->add_edge('q', 'r');
$g->add_edge('r', 's');

# what I'd like this to return is
# a, b, c, d, e
# c, q, r, s
# c, z
# see, since c is a branch point, I want c to be part of the set returned
# by the program.

# this current code starts at 'a' and cruises along the depth first tree
#  but it doesnt exhaustively find all the branches and produce the above
# output.

my $old_node;
my $count = 0;
my @pre;

#this returns all paths
#the call to print in post is only made at terminal nodes for each possible path from a branch
#at this point @pre is a complete path from start to the terminal node
#you can replace "print join()" with any desired action you want to perform on @pre, including making a copy
my $startnode = 'a';
my $t = Graph::Traversal::DFS->new($g,

				   pre  => sub {push @pre,$_[0]},
				   post  => sub {
				       print join(',',@pre),"\n" if($g->degree($_[0]) == 1 && $_[0] ne $startnode); 
				       pop @pre;},
				   next_alphabetic=>1, # if you want output order to be deterministic, otherwise will display paths in arbitrary order
				   start => $startnode);

$t->dfs;
print "\n";