What does “select((select(s),$|=1)[0])” do in Perl?

Question

I\'ve seen some horrific code written in Perl, but I can\'t make head nor tail of this one:

select((select(s),$|=1)[0])

It\'s in some netwo

Answer 1

select($fh)

Select a new default file handle. See http://perldoc.perl.org/functions/select.html

(select($fh), $|=1)

Turn on autoflush. See http://perldoc.perl.org/perlvar.html

(select($fh), $|=1)[0]

Return the first value of this tuple.

select((select($fh), $|=1)[0])

select it, i.e. restore the old default file handle.

---

Equivalent to

$oldfh = select($fh);
$| = 1;
select($oldfh);

which means

use IO::Handle;
$fh->autoflush(1);

as demonstrated in the perldoc page.