fallback/const-xs.inc
25:          sv = sv_2mortal(newSVpvf("%s is not a valid Sys::Syslog macro", s));

const-xs.inc
299:	    sv = newSVpvf("%"SVf" is not a valid Sys::Syslog macro",

t/constants.t
16:like( $@, "/^This is not a valid $testpack macro/", "trying a non-existing macro");
19:like( $@, "/^NOSUCHNAME is not a valid $testpack macro/", "trying a non-existing macro");

Syslog.pm
574:    if (index($value, "not a valid") >= 0) {
580:    $value = -1 if index($value, "not a valid") >= 0;

Syslog.c

 803 sub connect_native {
 804     my ($errs) = @_;
 805     my $logopt = 0;
 806
 807     # reconstruct the numeric equivalent of the options
 808     for my $opt (keys %options) {
 809         $logopt += xlate($opt) if $options{$opt}
 810     }

/*
 * Option flags for openlog.
 *
 * LOG_ODELAY no longer does anything.
 * LOG_NDELAY is the inverse of what it used to be.
 */
#define LOG_PID         0x01    /* log the pid with each message */
#define LOG_CONS        0x02    /* log on the console if errors in sending */
#define LOG_ODELAY      0x04    /* delay open until first syslog() (default) */
#define LOG_NDELAY      0x08    /* don't delay open */
#define LOG_NOWAIT      0x10    /* don't wait for console forks: DEPRECATED */
#define LOG_PERROR      0x20    /* log to stderr as well */

 100 my %options = (
 101     ndelay  => 0,
 102     noeol   => 0,
 103     nofatal => 0,
 104     nonul   => 0,
 105     nowait  => 0,
 106     perror  => 0,
 107     pid     => 0,
 108 );

 156 # coderef for a nicer handling of errors
 157 my $err_sub = $options{nofatal} ? \&warnings::warnif : \&croak;

 149 # Perl 5.6.0's warnings.pm doesn't have warnings::warnif()
 150 if (not defined &warnings::warnif) {
 151     *warnings::warnif = sub {
 152         goto &warnings::warn if warnings::enabled(__PACKAGE__)
 153     }
 154 }