If you just want to add dots then combine switching off buffering output with not printing "\n"

$|=1;

[some loop condition]
    print ".";
    [do other stuff]
[end loop]
[download]

This will print dots next to each other which maybe close to what you are asking for.
Depending on what you are doing you may only want to print a dot every n iterations

$|=1;
$counter=0;

[some loop condition]
     print "." unless $count++ % n;
     [do other stuff]
[end loop]
[download]