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

while (<DATA>)
{
	chomp; # avoid matching against newline
	my $words = join "=>", parse_csv($_);
	print "$words\n";
}

sub parse_csv
{
	my $text = shift;      # record containing comma-separated values
	my @new = ( );
	
	push @new, $+ while $text =~ m{
		\s*"([^\"\\]*(?:\\.[^\"\\]*)*)"\s*,?	# Matches a phrase that may contain commas
		| \s*([^,]+)\s*,?	# Something that is not a comma
		| \s*,	# Just a comma - no data
		}gx;

	push (@new, undef) if substr($text, -1,1)eq ',';
	return @new;
}

__DATA__
1,the,simple,case
"with","quoted" , "strings that contain spaces"
"with","quoted" , "comma, internally"
"with","quoted" , "comma, internally, with null data",,,