use 5.004;
    use Fcntl qw(:DEFAULT :flock);
    open(FH, '<', $file)  or die "can't open $file: $!";
    unless (flock(FH, LOCK_SH | LOCK_NB)) {
	local $| = 1;
	print "Waiting for lock...";
	flock(FH, LOCK_SH)  or die "can't lock $file: $!";
	print "got it.\n"
    } 
    # now read from FH