In principle your regex works, but probably your string on which you want to substitute doesn't contain what you think it does.

Here's an example of reading the data in paragraph mode (see $/ for an explanation) and then applying your regex: 

use strict;
use warnings;

local $/ = "";

while (<DATA>){
    chomp;
    s/\n/,/g;
    print "$_\n";
}

__DATA__
1111
2222
3333

4444
5555
6666

[download]

In reply to Re: how to convert new line to "," by moritz
in thread how to convert new line to "," by bh_perl

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