use Graph;
use Data::Dumper;
use strict;
use warnings;

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

my $g = new Graph edges => [ map [ split /,/ ], @pairs ];

my @av = map [ map { my $v = $_; map [$v,$_], $g->successors($v) } @$_ ], $g->weakly_connected_components;

print Dumper @av;