hash_foo.pp

# This class foos a hash.
#
# @example format:
#    class {'hash_foo':
#      foo                 => {
#        'acquaintance_name' => {
#          'command' => '/path/to/command',
#          'frequency' => 'rarely',
#          'oneoff' => true,
#        }
#     }
#
# @param foo The hash to be food.
# @param bar Where to meet.
#
class hash_foo (
  Hash $foo,
  String $bar = 'Cheers',
) {
# ...
}

hash_foo2.pp

# This class foos a hash.
#
# @example format:
#    class {'hash_foo':
#      foo                 => {
#        'acquaintance_name' => {
#          'command' => '/path/to/command',
#          'frequency' => 'rarely',
#          'oneoff' => true,
#        }
#     }
#
# @param foo The hash to be food.
# @param bar Where to meet.
#
class hash_foo (
  Hash[String, Hash_foo::Foo] $foo,
  String $bar = 'Cheers',
) {
# ...
}

types__foo.pp

type Hash_foo::Foo = Struct[{
  $command   => Stdlib::Absolutepath,
  $frequency => Enum['rarely', 'always'],
  $oneoff    => Boolean,
}]