int conn = socket(.....);

[...]

ENTER;
SAVETMPS;
PUSHMARK(SP);
XPUSHs(sv_2mortal(newSViv(conn)));
PUTBACK;
cpretval = call_sv(the_coderef, G_SCALAR|G_EVAL|G_KEEPERR);
SPAGAIN;
if(SvTRUE(ERRSV)) {
    STRLEN n_a;
    log_helper(1,kidno,SvPV(ERRSV, n_a));
    POPs;
    real_retval = 0;
}
else {
    if(cpretval != 1)
        croak("Return count from coderef callback != 1");

    real_retval = POPi;
}
PUTBACK;
FREETMPS;
LEAVE;



##</code><code>##

sub the_callback_function {
  my ($conn) = @_;

  open(my $c,"+<&=$conn");
  bless $c, 'IO::Socket::INET';
  $c->autoflush(1);
  $c->send("Network data!\n");
  .....

##</code><code>##

PerlIO* conn_pio;
conn_pio = PerlIO_fdopen(conn,"r+");