gistfile1.pl

use strict;
use warnings;

use v5.16;

use Graph::Directed;

my $g = Graph::Directed->new();
$g->add_edge( A => 'B' );
$g->add_edge( B => 'D' );
$g->add_edge( C => 'D' );
$g->add_edge( D => 'E' );
$g->add_edge( A => 'E' );

my @steps;

sub _follow {
    my $target = shift;

    my @p = $g->predecessors($target)
        or return;
    unshift @steps, \@p;

    _follow($_) for @p;
}

_follow('E');

use Devel::Dwarn; Dwarn \@steps;