use Inline 'C';

my $str = string1();
print $str;
my $retval = string2($str);
print $str, "And the answer is $retval\n";

__END__
__C__

/* Reset the stack and push SV* onto it */
void string1() {
    char * set = "Hello \0";
    dXSARGS;
    sp = mark;
    XPUSHs(sv_2mortal(newSVpv(set,strlen(set))));
    PUTBACK;
}

/* Modify passed SV* C style, also return an int */
int string2( SV * str ) {
   char * set = "World!\n\0";
   sv_setpvn( str, set, strlen(set) ); 
  return 42;
}