Looking at the source, the inputs to openTee must be a glob (ref(\$file) eq 'GLOB'), a string expression starting with ">" or ">>", or a file name (opened for append).

Based on some quick testing (without the module), all of these should work 

local *LOG;
open(LOG, '>>test.out');
openTee(*STDOUT, *STDOUT, *LOG);

my $fh = IO::File->new(">>test.out");
openTee(*STDOUT, *STDOUT, *$fh);

open(my $fh, '>>', 'test.out');
openTee(*STDOUT, *STDOUT, *$fh);

openTee(*STDOUT, *STDOUT, '>>test.out');

openTee(*STDOUT, *STDOUT, 'test.out');

[download]

By the way, why do you want to use IO::File instead of open anyway?

In reply to Re: Problems with Filehandles and TeeOutput by ikegami
in thread Problems with Filehandles and TeeOutput by hkpatv

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