Some possible debugging advice:

are you printing the content header?

  print "Content-type: text/html\n\n";

turn on warnings:  (use -w)

use strict;


die "File not found unless" -f $config;
open(CON,$config) || die $!;
my $list = join '', <CON>;
...
open(CONOUT, ">$config") || die $!;

Also consider using flock, or using some other 
configuration method (berkely DB [DB_File] or XML [xml::Simple] )