Um ... I'll bite. Why can't you install anything from CPAN?

while (<FILE>)
{
  chomp;
  s/^\s+//;
  s/#.*//;
  s/\s+$//;

  next unless length;

  if (/^(.*?\S)\s*=\s*(.*)$/)
  {
    push @{$CONFIG{$key}}, $val;
  }
}
[download]

The only thing that makes sense to me is storing an array reference in the hash if you're going to do it by hand. I took the liberty of making a few minor changes.