#!/usr/bin/perl
use strict;
use warnings;

use JSON::XS;

my $json = '{"feed":{"updated":{"$t":"2019-07-19T20:04:56.046Z"}}}';
my $decoded_json = decode_json($json);
print $decoded_json->{feed}->{updated}->{'$t'};  # 2019-07-19T20:04:56.046Z