You have to change the record separator to "\r\n"

use strict;
use warnings;
use 5.010;

my $text = "field\n1,field2,field3\r\nfield4,field\n5,field6\n\r\n";
open my $fh, '<', \$text;
local $/ = "\r\n";

while (<$fh>) {
    chomp;
    my ( $col1, $col2, $col3 ) = split ',';
    say "|$col1 $col2 $col3|";
}
[download]

Of course when you print it you'll see the new lines, if you don't want that either you can replace them.