## From Socket.pm (Fnctl.pm contains an nearly identical sub)
sub AUTOLOAD {
    my($constname);
    ($constname = $AUTOLOAD) =~ s/.*:://;
    croak "&Socket::constant not defined" if $constname eq 'constant';
    my ($error, $val) = constant($constname);
    if ($error) {
	croak $error;
    }
    *$AUTOLOAD = sub { $val };
    goto &$AUTOLOAD;
}