use warnings;
use strict;
use strict;
use warnings;
use CGI qw(:standard);
use CGI::Carp qw(warningsToBrowser fatalsToBrowser);

my $file2 = <<DATA;
0001,Nunki 2 1,5847,71%,0.71,4151.37,ThrevenGuard,-18,-26
0003,Nunki 2 3,5000,50%,0.5,2500,Honor,-21,-13
0004,Nunki 2 4,4692,39%,0.39,1829.88,Honor,-40,-17
0005,Nunki 2 5,2615,24%,0.24,627.6,Bananiel,-44,-47
0006,Sagittarius 2 1,5000,50%,0.5,2500,Riley Prime,20,-30
0007,Sagittarius 2 2,4731,38%,0.38,1797.78,Bananiel,11,-25
0008,Sagittarius 2 3,6949,18%,0.18,1250.82,Litex,16,-44
0009,Sagittarius 2 4,3004,52%,0.52,1562.08,Bananiel,4,-21
0010,Sagittarius 2 5,3414,75%,0.75,2560.5,5r22,0,-45
0011,Sagittarius 2 6,6146,29%,0.29,1782.34,Bananiel,4,-11
0012,Sagittarius 2 7,6564,61%,0.61,4004.04,dJ,44,-32
0013,Rigel 2 1,6870,30%,0.3,2061,Black_Dragon,-44,95
0014,Rigel 2 2,5000,50%,0.5,2500,Black_Dragon,-35,102
0015,Rigel 2 3,2854,51%,0.51,1455.54,unoccupied
0016,Rigel 2 4,6247,28%,0.28,1749.16,DaSnake,-56,105
0018,Rigel 2 6,4160,59%,0.59,2454.4,Khouri,-49,75
0019,Rigel 2 7,5801,18%,0.18,1044.18,Honor,-69,103
0020,Fornacis 2 1,2409,56%,0.56,1349.04,Mariska,25,51
0021,Fornacis 2 2,5000,50%,0.5,2500,Bananiel,32,44
0022,Fornacis 2 3,6998,32%,0.32,2239.36,Riley Prime,23,35
0023,Fornacis 2 4,5483,52%,0.52,2851.16,Riley Prime,33,33
0024,Fornacis 2 5,5999,63%,0.63,3779.37,Perkins,26,67
0025,Fornacis 2 6,3038,38%,0.38,1154.44,Riley Prime,10,29
DATA
my $file1 = <<DATA;
0001,Nunki 2 1,5847,71%,0.71,4151.37,ThrevenGuard,-18,-26
0002,Nunki 2 2,6366,59%,0.59,3755.94,Honor,-23,-19
0003,Nunki 2 3,5000,50%,0.5,2500,Honor,-21,-13
0004,Nunki 2 4,4692,39%,0.39,1829.88,Honor,-40,-17
0006,Sagittarius 2 1,5000,50%,0.5,2500,Riley Prime,20,-30
0007,Sagittarius 2 2,4731,38%,0.38,1797.78,Bananiel,11,-25
0008,Sagittarius 2 3,6949,18%,0.18,1250.82,Litex,16,-44
0009,Sagittarius 2 4,3004,52%,0.52,1562.08,Bananiel,4,-21
0010,Sagittarius 2 5,3414,75%,0.75,2560.5,Iridium,0,-45
0011,Sagittarius 2 6,6146,29%,0.29,1782.34,Bananiel,4,-11
0012,Sagittarius 2 7,6564,61%,0.61,4004.04,dJ,44,-32
0015,Rigel 2 3,2854,51%,0.51,1455.54,Bananiel,-30,96
0016,Rigel 2 4,6247,28%,0.28,1749.16,DaSnake,-56,105
0019,Rigel 2 7,5801,18%,0.18,1044.18,ThrevenGuard,-69,103
0020,Fornacis 2 1,2409,56%,0.56,1349.04,Mariska,25,51
0021,Fornacis 2 2,5000,50%,0.5,2500,Bananiel,32,44
0022,Fornacis 2 3,6998,32%,0.32,2239.36,Riley Prime,23,35
0023,Fornacis 2 4,5483,52%,0.52,2851.16,unoccupied
0024,Fornacis 2 5,5999,63%,0.63,3779.37,Perkins,26,67
0025,Fornacis 2 6,3038,38%,0.38,1154.44,Riley Prime,10,29
DATA

#create data files
open outFile, "> file1.txt";
print outFile $file1;
close outFile;

open outFile, "> file2.txt";
print outFile $file2;
close outFile;

#OP's code
print "Cache-Control: max-age=30\n";

my %final;
my %compare1;
my %compare2;
my $maxid = "2000";

open(DAT,"file1.txt");
my @data = <DAT>;
close(DAT);
for(my $i = 0; $i < scalar(@data); $i++) {    # dump file data into hashed array
    my $id = substr($data[$i], 0, 4);    # get current planet id
    $compare1{$id} = $data[$i];
    delete $data[$i];
}
@data = ();

open(DAT,"file2.txt");
@data = <DAT>;
close(DAT);
for(my $i = 0; $i < scalar(@data); $i++) {    # dump file data into hashed array
    my $id = substr($data[$i], 0, 4);    # get current planet id
    $compare2{$id} = $data[$i];
    delete $data[$i];
}
@data = ();

open(DAT,">parsed-all.txt");    # open appropriate parsed file and clear it
close(DAT);
for(my $i = 1; $i <= $maxid; $i++) {
    my $currid = changeID($i);
    next if ! defined $compare1{$currid} and ! defined $compare2{$currid};
    next if defined $compare1{$currid} and defined $compare2{$currid}
      and $compare1{$currid} eq $compare2{$currid};

    open(DAT,">>parsed-all.txt");
    if (defined $compare1{$currid})
      {print DAT $compare1{$currid};}
    else
      {print DAT $compare2{$currid};}
    close(DAT);
    delete $compare1{$currid};
    delete $compare2{$currid};
}
exit;

sub changeID {
return sprintf "%04d", $_[0];
}