$ perl -E'
   local *STDOUT;
   open STDOUT, ">&", 1 or die;
   open my $fh, ">&=", 1 or die;
   say $fh "test";
   say $fh == STDOUT || 0;
   say $fh eq STDOUT || 0;
   say $fh == *STDOUT || 0;
   say $fh eq *STDOUT || 0;
   say fileno($fh) == 1 || 0;
   say fileno($fh) == fileno(STDOUT) || 0;
'
test
0
0
0
0
1
0