use SelectSaver;

select $fh_old;
{
    my $saver = new SelectSaver($fh_new); # selects $fh_new
}
# block ends; object pointed to by "my" $saver is destroyed
# previous handle, $fh_old is now selected

# alternative invocation, without file handle argument
my $saver = new SelectSaver; # selected file handle remains unchanged