use vars qw($idnum);

sub unique
{
    my $remote_addr = sprintf '%02X%02X%02X%02X', (split /\./, $ENV{'REMOTE_ADDR'});
    unless(++$idnum < 0x10000) { sleep 1; $idnum = 0; }
    return sprintf '%012X.%s.%08X.%04X', time, $remote_addr, $$, $idnum;
}