I'm not exactly sure of your requirements - you would be better off to provide some simple/minimalist test program that demonstrates what you're attempting to achieve. (Since you have not yet worked out how to achieve what you're after, that test script would presumably not work - but if it gave us some hints regarding the essence of your aims, that might help.)

Here's a basic, contrived example of how the return values of C functions (namely, the foo() and bar() functions) could be fed into the embedded perl process. It's just a slight modification of the 'power.c' example from perlembed:

 
#include <EXTERN.h>
#include <perl.h>

static PerlInterpreter *my_perl;

static void
PerlPower(int a, int b)
{
  dSP;                           
  ENTER;                         
  SAVETMPS;                      
  PUSHMARK(SP);                  
  XPUSHs(sv_2mortal(newSViv(a)));
  XPUSHs(sv_2mortal(newSViv(b)));
  PUTBACK;                      
  call_pv("expo", G_SCALAR);    
  SPAGAIN;                      
                                
  printf ("%d to the %dth power is %d.\n", a, b, POPi);
  PUTBACK;
  FREETMPS;
  LEAVE;  
}

int foo(void) {
    unsigned long t = (unsigned)time( NULL );
    return (t % 5) + 3;
}

int bar(void) {
    unsigned long t = (unsigned)time( NULL );
    return (t % 4) + 2;
}

int main (int argc, char **argv, char **env)
{
  char *my_argv[] = { "", "power.pl" };

  PERL_SYS_INIT3(&argc,&argv,&env);
  my_perl = perl_alloc();
  perl_construct( my_perl );

  perl_parse(my_perl, NULL, 2, my_argv, (char **)NULL);
  PL_exit_flags |= PERL_EXIT_DESTRUCT_END;
  perl_run(my_perl);

  PerlPower(foo(), bar()); /* foo() ** bar() */

  perl_destruct(my_perl);
  perl_free(my_perl);
  PERL_SYS_TERM();
}
[download]

For that program to work, 'power.pl' needs to be also in the cwd - and needs to contain the following:

sub expo {
  my ($a, $b) = @_;
  return $a ** $b;
}
[download]

Cheers,
Rob