You can force print() to print unbuffered like this:

$| = 1;
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perl -e 'use v5.10; $| = 1; for (1..10) {print $_; sleep(1);}'
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I was looking for a link to the docs to share with you and found this oldie but goodie from the Perl Cookbook: Recipe 7.19. Flushing Output :-)

Hope this helps!