G'day OrdinaryFIlmmaker,

Welcome to the Monastery.

It would've helped if you'd read "How do I post a question effectively?" before posting. Providing your data as paragraph (<p>) text does not allow us to see what it really is: HTML will, amongst other things, convert sequences of whitespace to a single space. We might have got clues from your code, but you didn't post that.

Here's what your input data looked like (newlines are represented by '$'s):

$ cat -vet pm_11118005_data
Eli Stern,,, $
10-Nov-19,,, $
1 subscriber,,, $
,,, $
Abdessamed Ham,,, $
15-Nov-19,,, $
0 subscribers,,, $
,,, $
Arne Martinson,,, $
22-Nov-19,,, $
0 subscribers,,, $
,,, $
[download]

Your wanted output is also questionable: space before 1st date but not the others; and, records ending with 2 commas, a space, and a newline.

Except for the dodgy space before the 1st date, this code produces the output you asked for:

#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

{
    open my $fh, '<', 'pm_11118005_data';
    local $/ = "\n,,, \n";
    while (<$fh>) {
        chomp;
        print join(',', $., split(/,,, \n?/)), ",, \n";
    }
}
[download]

Output:

1,Eli Stern,10-Nov-19,1 subscriber,, 
2,Abdessamed Ham,15-Nov-19,0 subscribers,, 
3,Arne Martinson,22-Nov-19,0 subscribers,,
[download]