Why not

sub _print {
  print $msg, @_;
  print LOG $msg, @_;
}

_print("hello");
_print("world");
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That way, you can print lists, and $, and $\ will be obeyed. OTOH, the simplest solution is probably the following:

use IO::Tee ();

my $fh_out = IO::Tee->new(\*STDOUT, \*LOG);
select($fh_out);

print("hello");
print("world");
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But there are problems with using select.