Re: .1 - Yes, I've been there. That confirms that h_errno is returned in $?. I don't see where to get the netdb.h constants or strings. All the detail is about the case where it returns subprocess exit status -- not the value of h_errno.

Re: .2 - Thanks, but Errno.pm gives the symbolic equivalents of the errno variable. I'm looking for symbolic constants for h_errno. Note the leading h_ - this is the errno-like variable used by the network information database routines.