use warnings;
use strict;

use Inline C => Config =>
    BUILD_NOISY => 1;

use Inline C => <<'EOC';

SV * create_undef() {
     return newSVsv(&PL_sv_undef);
} 

void is_defined(SV * x) {
     //x = &PL_sv_undef;
     x == &PL_sv_undef ? printf("Not defined\n") : printf("Defined\n");
}

EOC

my $undef = create_undef();
is_defined($undef);