#!/usr/bin/perl

use strict;

my $Usage = "Usage: $0 old_file  new_file  > union_file\n";
die $Usage unless ( @ARGV == 2 and -f $ARGV[0] and -f $ARGV[1] );

my %union;

open IN, $ARGV[0] or die "$ARGV[0]: $!";
while (<IN>) {
    chomp;
    my @flds = split /,/;
    my $val = pop @flds;  # assumes exactly 4 fields in every row
    my $key = join ',', @flds;
    $union{$key} = $val;
}
open IN, $ARGV[1] or die "$ARGV[1]: $!";
while (<IN>) {
    chomp;
    my @flds = split /,/;
    my $val = pop @flds;
    my $key = join ',', @flds;

    next if ( exists( $union{$key} ) and
             abs(($union{$key} - $val)/$union{$key}) * 100 > 1 );

    $union{$key} = $val;
}

# union is now complete

print "$_,$union{$_}\n" for ( sort keys %union );