The following program downloads a file very slowly. Maybe this gets you started.

#!/usr/bin/perl -w
use strict;
use WWW::Mechanize;
use 5.020;
use feature 'signatures';
no warnings 'experimental::signatures';

my $mech = WWW::Mechanize->new();

my $large_url = 'http://ftp.acc.umu.se/mirror/wikimedia.org/dumps/dewi
+ki/20220420/dewiki-20220420-abstract.xml.gz';

$| = 1;

my $read_size = 0;
$mech->get(
    $large_url,
    ':read_size_hint' => 4096,
    ':content_cb' => sub {
        $read_size += length( $_[0] );
        my $len = length($_[0]);
        print "\r$len - $read_size bytes";
        # discard the content
        sleep 1;
    },
);

say 'done';
[download]