I don't understand why $|++ is universally preferred (or at least so it seems to me) over the more straightforward $|=1. What's the reason?

Perhaps your "Perl Sense" is underdeveloped? $var++ can be either a counter or a boolean. It's the context that's important (as with so many things in Perl). I'd wager that most Perlers distinguish between the use of ++ and how the object is used.

If you feel the need to be explicit, you might like this:

use IO::Handle;
STDOUT->autoflush(1); # OO form
autoflush STDOUT 1;   # procedural form
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