return if defined($n); # likely
croak "sendmsg: $! (check RLIMIT_NOFILE)" if $!{ETOOMANYREFS};
croak "sendmsg: $!" if !$!{EMSGSIZE};
socketpair(my $r, my $w, AF_UNIX, SOCK_STREAM, 0) or
croak "socketpair: $!";
return if defined($n); # likely
croak "sendmsg: $! (check RLIMIT_NOFILE)" if $!{ETOOMANYREFS};
croak "sendmsg: $!" if !$!{EMSGSIZE};
socketpair(my $r, my $w, AF_UNIX, SOCK_STREAM, 0) or
croak "socketpair: $!";