I think there's some misunderstanding of what a duplicate filehandle does. What you have is very nice for closing the duplicates. It doesn't close the originals, though. Duplicate file handles to the same descriptor may share lock status, but they still open and close separately.

I did test this with 255 instead of 20 BTW, but you don't really need to see 255 warnings scroll by. There are fewer than 20 files open here, anyway. Just call it the "arbitrarily large" constant people have been tossing out.

If you really want to close by descriptor, use POSIX::close as suggested by BrowserUk at Re: how to close all files.

use strict;
use warnings;

open ( my $foo, '>&=', 1 );
close( STDOUT );
print STDOUT "foo!\n";
print $foo "foo!\n";

open ( my $bar, '>&=', $foo );
close $foo;
print $foo "foo!\n";
print $bar "bar!\n";

open ( my $baz, '>', 'files/baz' );
open ( my $quux, '>&=', $baz );
close $baz;
print $quux "quux!\n";

open ( $baz, '>>', 'files/baz' );
open ( $quux, '>>&=', $baz );
close $quux;
print $baz "baz!\n";

open ( my $prefork, '>', 'files/prefork.txt' );

if ( my $kidpid = fork ) {
    my $deadkid = wait();
    print $prefork "child was pid $deadkid, which thankfully matches $
+kidpid (we'd be worried if it didn't)\n";
} elsif ( defined $kidpid ) {
    for ( 0..20 ) {
        open ( my $postfork, '>>&=', $_ );
        close $postfork;
        print $postfork "Whee!\n";
    }
    print $prefork "Dupes are just copies!\n";
} else {
    print "I couldn't fork!\n";
}
[download]