Perl_do_shmio(pTHX_ I32 optype, SV **mark, SV **sp)
{
#ifdef HAS_SHM
    char *shm;
    struct shmid_ds shmds;
    const I32 id = SvIVx(*++mark);
    SV * const mstr = *++mark;
    const I32 mpos = SvIVx(*++mark);
    const I32 msize = SvIVx(*++mark);