then all your code which assumes stations have IP addresses which are arrayrefs of strings breaks again.

Nope. This:

#! perl -slw
use strict;
use Data::Dump qw[ pp ];
use XML::Simple;

my $xml = XMLin( \*DATA, ForceArray => [ 'ip' ], NoAttr => 1 );
pp $xml;

__DATA__
<servers>
    <station18>
        <ip>10.0.0.101</ip>
        <ip>10.0.1.101</ip>
        <ip>10.0.0.102</ip>
        <ip>10.0.0.103</ip>
        <ip>10.0.1.103</ip>
    </station18>
    <station19>
        <ip>10.0.0.111</ip>
        <ip>10.0.1.111</ip>
        <ip>10.0.0.112</ip>
        <ip>10.0.0.113</ip>
        <ip>10.0.1.113</ip>
    </station19>
    <station17>
        <ip assignment="temporary">10.0.0.101</ip>
        <ip>10.0.0.121</ip>
    </station17>
</servers>
[download]

Produces this::

C:\test>junk44
{
  station17 => { ip => ["10.0.0.101", "10.0.0.121"] },
  station18 => {
                 ip => [
                         "10.0.0.101",
                         "10.0.1.101",
                         "10.0.0.102",
                         "10.0.0.103",
                         "10.0.1.103",
                       ],
               },
  station19 => {
                 ip => [
                         "10.0.0.111",
                         "10.0.1.111",
                         "10.0.0.112",
                         "10.0.0.113",
                         "10.0.1.113",
                       ],
               },
}
[download]