The "#4" warnings in the following code produce no output in Perl 5.6 because STDERR is not open. The "#4" warnings do produce output in Perl 5.8 even though STDERR is not open. Is this documented somewhere? 
warn "#1: warning";
print "#1: STDOUT is open\n";
print STDERR "#1: STDERR is open\n";
warn "#1: warning";

open FILE, '>&STDOUT';
close STDOUT;

warn "#2: warning";
print "#2: STDOUT is open\n";
print STDERR "#2: STDERR is open\n";
warn "#2: warning";

close STDERR;

warn "#3: warning";
print "#3: STDOUT is open\n";
print STDERR "#3: STDERR is open\n";
warn "#3: warning";

open STDOUT, '>&FILE';
close FILE;

warn "#4: warning";
print "#4: STDOUT is open\n";
print STDERR "#4: STDERR is open\n";
warn "#4: warning";

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In reply to Perl 5.8: warn sometimes writes to STDOUT? by jdalbec

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