use IO::Handle qw( );

# Require a non-blocking handle.
# Returns undef on read error (Check $!)
sub is_ready_to_read {
   my ($fh) = @_;

   my $blocking = $fh->blocking(0);
   return undef if !defined($blocking);

   my $rv = _is_ready_to_read($fh);

   {
      local $!;
      local $^E;
      $fh->blocking($blocking);
   }

   return $rv;
}

sub _is_ready_to_read {
   my ($fh) = @_;
   return 1 if defined(eof($fh));
   return 0 if $!{EAGAIN} || $!{EWOULDBLOCK};
   return undef;
}