use IO::Tee;
use IO::File;

open(OLDOUT, ">&STDOUT");
open(OLDERR, ">&STDERR");
my $output_file = new IO::File(">tt1.out");
my $TeeOut = new IO::Tee(\*OLDOUT, $output_file);
my $TeeErr = new IO::Tee(\*OLDERR, $output_file);

open(STDERR, ">&", \*$TeeErr);
select(STDERR); $| = 1;
print $TeeErr "This goes to both STDERR and to the file.\n";
print STDERR "I would like this to do the same as above, but it goes nowhere.\n";