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

### Time span to be expired
use constant EXPIRES =>     60 * 60 * 24 * 365; # sec

### File extension part into MIME types
my %ext2mime = (
    'jpg'   => 'image/jpeg',
    'jpeg'  => 'image/jpeg',
    'gif'   => 'image/gif',
    'png'   => 'image/png',
);

### Document Root
my $script_filename = $ENV{'SCRIPT_FILENAME'};
my $script_name = $ENV{'SCRIPT_NAME'};
$script_filename =~ s!/\Q$script_name\E$!!;

### File Informations
my  $req_path = $script_filename. $ENV{'REQUEST_URI'};
my( $filepath ) = $req_path =~ m!^([^\?]+)!;
-f $filepath
	or die 'File not found';
my( $file_ext ) = $filepath =~ m!\.(.+?)$!;
$ext2mime{$file_ext}
	or die 'Invalid MIME type';

### Content Header
$|++;
my  $cur_time = time;
my  @filestat = stat $filepath;
printf "Date: %s\n",
	POSIX::strftime( '%a, %d %b %Y %T GMT', gmtime( $cur_time ) );
printf "Server: %s\n",
	$ENV{'SERVER_SOFTWARE'};
printf "Last-Modified: %s\n",
	POSIX::strftime( '%a, %d %b %Y %T GMT', gmtime( $filestat[9] ) );
printf "Expires: %s\n",
	POSIX::strftime( '%a, %d %b %Y %T GMT', gmtime( $cur_time + EXPIRES ) );
printf "Connection: %s\n",
	$ENV{'HTTP_CONNECTION'};
printf "Accept-Ranges: bytes\n";
printf "Content-Length: %d\n",
	$filestat[7];
printf "Content-Type: %s\n",
	$ext2mime{$file_ext};
printf "\n";

### Content Body
if( open( my $fh, "<$filepath" )) {
    binmode STDOUT;
    print STDOUT <$fh>;
    close $fh;
}