Puppet expansion of facts inside command strings requires double quoted string

Small gotcha for puppet facts. If you want a puppet fact to be expanded inside a quoted string you need to use double quotes (i.e. a ruby-style format string).

  exec { 'something':
    # This has to be a double quote for the fact to get expanded
    command     => "/usr/bin/something ${my_custom_fact}",
    refreshonly => 'true',
  }