Not true:

#!/usr/bin/perl -wT

use strict;
use warnings 'FATAL' => 'all';
use CGI ':standard';
use 5.010000;

$|++;

print header;
print start_html('Dots');

say 'One dot per second.<br>';
for ( 1 .. 30 ) {
    print '. ';
    sleep 1;
}

print end_html;
[download]

Runs here.

Update: Removed dead link.