That's not true. Even if he did it properly (say by adding next if @ready; before the first die), he'd see the same behaviour. waitpid unavoidably overwrites $!=EINTR with $!=ECHLD between the time select reports an error and the program checks the cause of the error.

...

use Errno qw( EINTR );

sub reaper {
   local ($!,$^E,$@);
   1 while waitpid -1,&POSIX::WNOHANG != -1;
   $SIG{CHLD} = \&reaper;
}

$SIG{CHLD} = \&reaper;

...

while (1) {
   my @ready = $select->can_read();
   if (!@ready) {
      next if $! == EINTR;
      die "select: $!";
   }

   handle($_) foreach @ready;
}
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Update: Added code.