{
   open local *STDOUT, '>', \$buf;
   ...
}

##</code><code>##

open TEMP, '>', \$buf;
my $old_select = select(TEMP);
...
select($old_select);

##</code><code>##

{
   my $old_select = select();
   my $handle = on_release { select($old_select); };
   open local *STDOUT, '>', \$buf;
   select(STDOUT);
   ...
}