The problem is that tha code you currently have to parse the form input

code:
----------------------------------------------------------------------
+----------
read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'});
@pairs = split(/&/, $buffer);
foreach $pair (@pairs) {
($name, $value) = split(/=/, $pair);
$value =~ tr/+/ /;
$value =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;

$value =~ s/\n/ /g;# added to strip line breaks 

$FORM{$name} = $value;
}
----------------------------------------------------------------------
+----------
[download]

does not handle multiple values. You should use the CGI module instead.
Replace the code above with code: --------------------------------------------------------------------------------

use CGI;
my $cgi = CGI->new();
[download]

--------------------------------------------------------------------------------
Then anywhere you would use $FORM{'parameter'} instead use $cgi->param('parameter')
See http://www.perldoc.com/perl5.8.0/lib/CGI.html for more details.