use strict;
use warnings;
use Data::Dumper;

my $text="";
while (<DATA>)
{
    $text.=$_;
    my @new;
    pos($text)=0;
    my $last=0;
    while ($text=~m{
        \G
        (?:
            "((?:[^"]+|"")*)"    # quoted section
        |
            ([^",]+)           # unquoted
        |
            ((?=\s*,))
        )
        (?:\s*,\s*|\s*\z)
    }gmx) {
        push (@new, $+);
        $last=$+[0];
        $new[-1]=~s/""/"/g;

    }
    if ($last==length($text)) {
        push (@new, "") if $text=~/,$/;
        print "Rec:".Data::Dumper->new([\@new])->Terse(1)
                                 ->Useqq(1)->Indent(0)->Dump()."\n";
        $text="";
    }
}
print "Error: $text\n" if $text;
__DATA__
1,the,simple,"case
"
"with","quoted" , "strings that contain spaces"
"with","quoted" , "comma,
internally"
"with","quoted" , "comma, internally, with ""null"" data",,,
""""""""