use strict;
use warnings;

use Inline C => Config =>
  BUILD_NOISY => 1,
  PRE_HEAD => "#define PERL_NO_GET_CONTEXT",
  ;

use Inline C => <<'EOC';

SV * dubble(SV * in) {
 dTHX;
 return newSViv(SvIV(in) * 2);
}

EOC

my $x = dubble(23);
print $x; # 46

##</code><code>##

#define PERL_NO_GET_CONTEXT

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"

SV * dubble(pTHX_ SV * in) {
 return newSViv(SvIV(in) * 2);
}

MODULE = FOO	PACKAGE = FOO	

SV *
dubble (in)
	SV *	in
CODE:
  RETVAL = dubble(aTHX_ in);
OUTPUT:
  RETVAL