In this case, I would strongly favour using or instead of '||'. It removes the need for the extra parens and is (IMO) visually cleaner too.

use File::Temp (qw/tempfile/);
($fh,$fname) = tempfile('quanta-XXXX')
    or die "Couldn't create temp file $fname\n";
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The (deliberately) much lower precedence of or means that it acts as an effective seperator between list contexts and in so doing, removes the need for a lot of otherwise necessary punctuation. TIMTOWTDI:)