On the machine I'm using right now (Windows 98), the behaviour of your code seems identical using perl v5.6.1 and perl v5.8.0. (I checked the output to STDOUT by redirecting the output to a file using >. This doesn't seem to capture output to STDERR as far as I can tell.) However, I have noticed some that on some other machines (also using Windows 98, but possibly not the same edition - but the same perl), the behavior of output to STDOUT and STDERR seems different (using identical code, of course.) For example, backquotes act differently - on one machine the code $result=`dir` causes the directory listing to be displayed on the screen, but $result isn't set!
I've always been perplexed about this. I am using binary makes of Perl that I downloaded via CPAN. I've wondered if the differences could be due to differences in how the various machines and/or OS editions implement shells; (there certainly are some differences when one goes to Windows XP.) This isn't a complete answer to your question, I know. If anyone has any comments about my remarks or the original poster's, I'd be very interested.
chas