anchor.diff:  Here's an example that will only write out configuration for the
   unixsocket tunable if a value was set by the user:
   
  -    {{~#if cfg.unixsocket}}
  +    {{#if cfg.unixsocket ~}}
       unixsocket {{cfg.unixsocket}}
  -    {{~/if}}
  +    {{/if ~}}
   
   > **Note** The `~` indicates that whitespace should be omitted when rendering
   
  
positive.code: 
  When writing your template, you can use the `with` helper to reduce duplication:
  
      {{#with cfg.repl}}
        repl-backlog-size {{backlog-size}}
        repl-backlog-ttl {{backlog-ttl}}
        repl-disable-tcp-nodelay {{disable-tcp-nodelay}}
      {{/with}}
  
  Helpers can also be nested and used together in block expressions. Here is another example from the redis.config file where the `if` and `with` helpers are used together to set up `core/redis` Habitat services  in a leader-follower topology.
  
      {{#if svc.me.follower}}
        slaveof {{svc.leader.sys.ip}} {{svc.leader.cfg.port}}
      {/if}}
  
  Here's an example using `each` to render multiple server entries:
  
      {{~#each cfg.servers as |server| }}
      server {
        host {{server.host}}
        port {{server.port}}
      }
      {{~/each}}
  
  You would specify the corresponding values in a TOML file using an
  [array of tables](https://github.com/toml-lang/toml#array-of-tables)
  
negative.code: 
      [[servers]]
      host = "host-2"
      port = 3434
  
  And for both `each` and `unless`, you can use `@first` and `@last` to specify which item in an array you want to perform business logic on. For example:
  
      "mongo": {
        {{#each bind.database.members as |member| ~}}
          {{#if @first ~}}
            "host" : "{{member.sys.ip}}",
            "port" : "{{member.cfg.port}}"
          {{/if ~}}
        {{/each ~}}
      }
  
  > **Note** The `@first` and `@last` variables also work with the Habitat helper `eachAlive`, and in the example above, it would be preferrable to the built-in `each` helper because it checks whether the service is available before trying to retrieve any values.
  
  For `unless`, using `@last` can also be helpful when you need to optionally include delimiters. In the example below, the IP addresses of the alive members returned by the `servers` binding is comma-separated. The logic check `{{#unless @last}}, {{/unless}}` at the end ensures that the comma is written after each element except the last element.
  
      {{#eachAlive bind.servers.members as |member| ~}}
        "{{member.sys.ip}}"
        {{#unless @last ~}}, {{/unless ~}} 
      {{/eachAlive ~}}]
  
  
  