#!/usr/bin/perl -w 
use strict;

{
    local $/; 
    my $line = <DATA>;
    $line =~ s/\n(?!\n)/, /g;
    $line =~ s/\n{2,}/\n/g;
    print $line;
}

__DATA__
!1,111
22,22?
.33,33//

4,444!!
::5,555
&&66,66



45,54@@
4,554<<
``4,654{

---
Output:
!1,111, 22,22?, .33,33//
, 4,444!!, ::5,555, &&66,66
, 45,54@@, 4,554<<, ``4,654{