my ($r_ready, $w_ready) = IO::Select::select($r_sel, $w_sel);

foreach my $sock (@$r_ready) {
   # Create alias to the appropriate buffer.
   our $buf; local *buf = \$in_bufs{$sock};

   my $rv = sysread($sock, $buf, 4096, length($buf));

   # Read error.
   if (not defined $rv) {
      $r_sel->remove($sock);
      # ... Handle error socket ...
      next;
   }

   # Socket EOF
   if (not $rv) {
      $r_sel->remove($sock);
      # ... Handle closed socket ...
      next;
   }

   for (;;) {
      # Search for a complete command.
      my $pos = index($buf, "\x0A");
      last if $pos < 0;

      my $cmd = substr($buf, 0, $pos+1, '');
      # ... process $cmd ...
   }
}

foreach my $sock (@$w_ready) {
   # ...
}