installed => {
    do => sub { shift->result($self->_is_installed) },
    rules  => [
      fail    => { "Postgres not\ninstalled" => sub {! shift->result }
+ },
      version => { "Postgres\ninstalled" => sub { shift->result } },
    ],
  },
[download]

Each rule now takes an optional hash reference. If supplied, the key is the "label" that appears on the line leading from state to state (take a look at the first state on the linked graph and notice the names.)

If you prefer, you can also specify the rules the old way:

    rules  => [
      fail    => sub { ! shift->result },
      version => sub { shift->result }
    ],
[download]

The only difference is that there is no label if a graph is generated. In other words, for rules you can use a subref or a hashref. Does that sound confusing? I think it is.

Can anyone suggest a cleaner syntax for the rule labels? Having state machine graphs auto-generated is really cool, but I don't know if it's worth the expense of making things too confusing to use. Because we're struggling with the syntax, we have not yet uploaded the version with GraphViz support.

As a side note, if you would prefer a completely different syntax for the module, we're open to anything that will make it easier to use, even though it's already pretty easy.