If you haven't "disabled" buffering {via HANDLE->autoflush(1), for example}, then your advice to lock won't really help much either (except that if you use Perl's own flock, it will flush the buffer before unlocking -- on modern versions of Perl).

Uhm, well, considering this forum is about Perl, I do assume we are talking about Perl's flock, not the one of some other language. As for modern Perls, 5.004 was released over 5 years ago. Annotating everything that has changed over the years isn't practical. Where do we stop? Early versions of perl required you to use do to call a sub. But I don't think it's very useful to say you need a modern version of Perl to call a sub without do.

Abigail