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

open my $csv1, "<csv1.csv";
open my $csv2, "<csv2.csv";
open my $csv3, ">csv3.csv";

my %csv1_data;
while (<$csv1>)
{
	if (/^(?<first>([^,]*,){3})(?<fields>([^,]*,){3}).*$/)
	{
		$csv1_data{$+{first}}=$+{fields};
	}
}

while (<$csv2>)
{
	if (/^(?<first>([^,]*,){3})(?<fields>([^,]*,){3})(?<rest>.*)$/)
	{
		if (defined $csv1_data{$+{first}})
		{
			print $csv3 "$+{first}$csv1_data{$+{first}}$+{rest}\n";
		}
		else
		{
			print $csv3 $_;
		}
	}
	
}