use Graph;

my @pairs=("a,b","c,b","d,f","e,b","f,g");

my $g = new Graph;

for ( @pairs )
{
	my($x,$y) = split /,/;
	$g->add_edge($x,$y);
}

my @subgraphs = $g->weakly_connected_components;

for my $subgraph ( @subgraphs )
{
	print "\nA subgraph:\n";
	for my $v ( @$subgraph )
	{
		my @s = $g->successors($v);
		print "  $v-$_\n" for @s;
	}
}