use Math::BigInt lib => 'GMP';
use warnings;
use strict;

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

use Inline C => <<'EOC';
      
void derivation(SV * obj) {
     if(sv_derived_from(obj, "Math::BigInt::GMP"))
       printf("A Math::BigInt::GMP object\n");
     else printf("Not a Math::BigInt::GMP object\n");

     if(sv_derived_from(obj, "Math::BigInt"))
       printf("A Math::BigInt object\n");
     else printf("Not a Math::BigInt object\n");
}

EOC

my $o = Math::BigInt->new(1234);
derivation($o);

__END__
Outputs:
Not a Math::BigInt::GMP object
A Math::BigInt object