As far as I can tell, you're looking for "topological sort".

Here's what I used: it's not very efficient, but good enough for my purposes.

# $set is a hashref containing all the objects you're sorting
# $connections_to is a hashref containing $from => $to pairs
# (i.e. $to is dependent on $from)

sub toposort {
  my ($set,$connections_to) = @_;
  my @order;
  while (%$set) {
    my ($start_node) =
      grep {!$connections_to->{$_} || !%{$connections_to->{$_}} }  val
+ues %$set;
    if (! $start_node ) {
      return;  # circular dependency found
    }
    push @order, $start_node;
    delete $set->{$start_node};
    delete $connections_to->{$_}->{$start_node} for keys %$connections
+_to;
  }
  return \@order;
}
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