Try it this way:

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

my %config;
while( <> ) {
    chomp;
    my @bits = split '[:|=]';
    my $ref = \%config;
    $ref = $ref->{ shift( @bits ) } //= {} while @bits > 2;
    $ref->{ pop @bits } = pop @bits;
}

pp \%config;
[download]

Produces:

C:\test>969796.pl 969796.dat
{
  "cfs_online_timeout_changes" => 200,
  "max_configured_packages" => 100,
  "max_reformation_duration" => 300,
  node => {
        nodeA => {
                   interface => {
                                  lan900 => {
                                              ip_address => { IP_A => 
+{ name => "IP_A", netmask => "255.255.255.0" } },
                                              name => "lan900",
                                              status => "up",
                                            },
                                  lan901 => {
                                              ip_address => { IP_C => 
+{ name => "IP_C", netmask => "255.255.255.0" } },
                                              name => "lan901",
                                              status => "up",
                                            },
                                },
                   name      => "nodeA",
                   status    => "up",
                   subnet    => {
                                  SUBNET_A => { name => "SUBNET_A", st
+atus => "up" },
                                  SUBNET_B => { name => "SUBNET_B", st
+atus => "up" },
                                },
                 },
        nodeB => {
                   interface => {
                                  lan900 => {
                                              ip_address => { IP_B => 
+{ name => "IP_B", netmask => "255.255.255.0" } },
                                              name => "lan900",
                                              status => "up",
                                            },
                                  lan901 => {
                                              ip_address => { IP_D => 
+{ name => "IP_D", netmask => "255.255.255.0" } },
                                              name => "lan901",
                                              status => "up",
                                            },
                                },
                   name      => "nodeB",
                   status    => "up",
                   subnet    => {
                                  SUBNET_A => { name => "SUBNET_A", st
+atus => "up" },
                                  SUBNET_B => { name => "SUBNET_B", st
+atus => "up" },
                                },
                 },
      },
}
[download]