#!/usr/bin/perl -Tw

use CGI;
use CGI::Carp qw/ fatalsToBrowser /;
use Fcntl;
use File::Basename;
use POSIX;
use strict;

$CGI::POST_MAX = 1048576;       #   Maximal file upload size
$CGI::DISABLE_UPLOADS = 0;

my $config = {
    'allowed_file_types'    =>  [ 
        'png', 
        'gif', 
        'jpg' 
    ],
    'upload_fields'         =>  [ 'image_file' ]
};

my $cgi = CGI->new;

foreach my $field ( @{ $config->{ 'upload_fields' } } ) {

    if ( defined $cgi->param( $field ) ) {

        my $fextension = ( fileparse( $cgi->param($field), '\..*' ) )[2];
        if ( grep { lc( $_ ) eq lc( $fextension ) } @{ $config->{ 'allowed_file_types' } } ) {

            my $fname;
            {
                local *FH;
                do {
                    $fname = tmpnam();
                } until sysopen ( FH, $fname, O_RDWR|O_CREAT|O_EXCL, 0666 );

                my $buffer;
                while ( read( $cgi->param( $field ), $buffer, 1024 ) ) {
                    syswrite FH, $buffer, length( $buffer );
                }
                close FH;
            }

            #   continue on and do stuff with uploaded file - file resides in temporary directory with file name $fname

        } else {

            #   bad file extension

        }
    }
}