#!/usr/bin/perl -w

use strict;
use warnings;
use JSON;
use LWP::UserAgent;
require HTTP::Cookies;
my $netloc = "xxx.xx.xx.xx:80";
my $realm = "Realm";
my $user = "username";
my $pass = "password";
my $auth_token = "token code";
my $ua = new LWP::UserAgent;
$ua->agent('Mozilla/5.0');
my $cookie_jar = HTTP::Cookies->new( file => 'cookies_lwp.txt', autosa
+ve => 1, ignore_discard => 1 ); 
$ua->cookie_jar($cookie_jar);
$ENV{PERL_LWP_SSL_VERIFY_HOSTNAME}=0;
$ua->default_header( "Authorization" => "Bearer $auth_token");
$ua->default_header( "Accept" =>"application/json"  );
$ua->default_header( "Content-Type" =>  "application/json");
$ua->credentials( $netloc, $realm, $user, $pass);
$ua->ssl_opts( verify_hostname => 0, SSL_verify_mode => 0x00);
my $request = new HTTP::Request('GET','https://xxx.xx.xx.xx/api/v2/dev
+ices/00:04:56:22:51:32/performance/?start_time=2022-02-15T10:00:00&st
+op_time=2022-02-16T10:00:00');

my $response = $ua->request($request);


if ($response->is_success) {
    my $output = $response->decoded_content;
    #print $output."\n";
    
#Code from perlmonks        
use JSON::PP;
my $data = join '', $output;
my $hashref = JSON::PP->new->decode($data);
use Data::Dump 'dd'; dd $hashref;

}
else {
    print STDERR $response->status_line, "\n";
}
[download]

Subroutine main::encode_json redefined at /usr/local/share/perl5/Expor
+ter.pm line 66.
 at ./wifi-api-get.pl line 33.
Subroutine main::decode_json redefined at /usr/local/share/perl5/Expor
+ter.pm line 66.
 at ./wifi-api-get.pl line 33.
Prototype mismatch: sub main::decode_json ($) vs none at /usr/local/sh
+are/perl5/Exporter.pm line 66.
 at ./wifi-api-get.pl line 33.
Subroutine main::from_json redefined at /usr/local/share/perl5/Exporte
+r.pm line 66.
 at ./wifi-api-get.pl line 33.
Prototype mismatch: sub main::from_json ($@) vs ($) at /usr/local/shar
+e/perl5/Exporter.pm line 66.
 at ./wifi-api-get.pl line 33.
Subroutine main::to_json redefined at /usr/local/share/perl5/Exporter.
+pm line 66.
 at ./wifi-api-get.pl line 33.
Prototype mismatch: sub main::to_json ($@) vs ($) at /usr/local/share/
+perl5/Exporter.pm line 66.
 at ./wifi-api-get.pl line 33.
{
  data   => [
              {
                mac => "00:04:56:22:51:32",
                managed_account => "",
                mode => "ap",
                name => "Espat AP3",
                network => "Belize City ePMP",
                online_duration => 3600,
                radio => {
                  dl_frame_utilization => 53.50833,
                  dl_kbits => 218936297,
                  dl_pkts => 24533891,
                  dl_retransmits_pct => 3.7125,
                  dl_throughput => 60611.05917,
                  ul_kbits => 11781720,
                  ul_pkts => 10095078,
                  ul_retransmits_pct => 1.7481,
                  ul_throughput => 3261.45,
                },
                sm_count => 45,
                sm_drops => 1,
                timestamp => "2022-02-15T04:00:00-06:00",
                tower => "Espat Twr",
                type => "epmp",
                uptime => 3600,
              },
              {
                mac => "00:04:56:22:51:32",
                managed_account => "",
                mode => "ap",
                name => "Espat AP3",
                network => "Belize City ePMP",
                online_duration => 3600,
                radio => {
                  dl_frame_utilization => 55.79167,
                  dl_kbits => 228622837,
                  dl_pkts => 25268171,
                  dl_retransmits_pct => 3.4875,
                  dl_throughput => 63241.6925,
                  ul_kbits => 11064503,
                  ul_pkts => 10404746,
                  ul_retransmits_pct => 1.6548,
                  ul_throughput => 3060.63917,
                },
.
.
.
.
rest of the output similar to your output.
[download]

You've used both JSON and JSON::PP in your code; don't do that. The former is a "smart" module that will pick the faster available backend between the pure perl version and JSON::XS if available. Since the first import has already pulled in the subs named when the second use is encountered perl is warning you that you're redefining things it already knows about.

The cake is a lie.
The cake is a lie.
The cake is a lie.