I don't think that's the problem. Using parenthesis is perfectly OK. You have to watch out when you leave them out:

close MAIL || die "couldn't close: $!"; # oops!
close MAIL or die "couldn't close: $!"; # correct

close(MAIL) || die "couldn't close: $!"; # correct (original post)
close(MAIL) or die "couldn't close: $!"; # correct as well
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The point here is operator precedence. In the wrong example the || binds tighter than 'close'. That's why the low precedence logical operators (and, or, not, xor) were introduced.

-- Hofmator