puppet - accessing items of an array within a hash from an erb template

gistfile1.txt

I'm having trouble iterating over an array, that's been retrieved from a hash. Here's the hash definition in the node manifest:

$alias_ips = {
  24 => [
    '10.254.16.82/24',
  ],
}

This hash is passed as a parameter to a named type, which in turn processes an erb template 
as part of a File definition. The erb file contains:

<%   unless alias_ips == :undef -%>
  <%  ips = alias_ips[number] -%>
  <%= ips.inspect %>
  <%= ips.class %>
<%   end -%>

The above executes and puts the following in the resulting file:

    ["10.254.16.82/24"]
  Array

Now, if I try and iterate through each item in this array like this:

<%   unless alias_ips == :undef -%>
  <%  ips = alias_ips[number] -%>
  <%= ips.inspect %>
  <%= ips.class %>
  <%  ips.each do |ip| -%>
    <%= ip %>
  <%  end -%>
<%   end -%>

then I get the following error trying to apply the manifest:

err: Could not retrieve catalog from remote server: Error 400 on SERVER: Failed to parse 
template network/types/bonded_vlan/interfaces_precise.erb: undefined method `each' for 
nil:NilClass at /etc/puppet/modules/network/manifests/type/bonded_vlan.pp:21 on node foo.example.com

So, given its getting an Array for the variable 'ips', how come .each doesn't work? 

Trying to get ips.size yields this error:

** [out :: bpsyd07-pmdh-collectd-02.inf.bulletproof.net] err: Could not retrieve catalog from remote server: Error 400 on SERVER: Failed to parse template network/types/bonded_vlan/interfaces_precise.erb: undefined method `size' for nil:NilClass at /etc/puppet/modules/network/manifests/type/bonded_vlan.pp:21 on node bpsyd07-pmdh-collectd-02.inf.bulletproof.net